Osteoblast Mineralization Research Articles

ZFP36, an RNA-binding protein promotes hBMSCs osteogenic differentiation via binding with JUN.

Osteoporosis (OP) is a metabolic bone disease characterized by progressive decline of bone mass and bone quality, leading to bone fragility and an increased risk of fracture. The osteogenic differentiation of bone mesenchymal stem cells (BMSCs) is crucial to maintain the balance of osteoblast and osteoclast. Bioinformatics prediction indicates that ZFP36 ring finger protein (ZFP36), an RNA-binding protein, is a potential target of OP. Herein, we sought to probe the regulatory role and mechanisms of ZFP36 in the progression of OP. Overexpression of ZFP36 enhanced osteoblast viability, differentiation and mineralization of human BMSCs (hBMSCs). RNA immunoprecipitation qPCR (RIP-qPCR) assays demonstrated that ZFP36 could inhibit the translation of JUN, which was also verified with dual luciferase reporter gene assay. Furthermore, administration with T-5224, a transcription factor c-Fos/activator protein (AP)-1 inhibitor, which specifically inhibits the DNA binding activity of c-Fos/JUN, abolished the effect of ZFP36 knockdown on the behaviors of hBMSCs, suggesting that ZFP36 might promotes osteogenic differentiation through regulating JUN. These findings provide insights into the progression and a potential therapeutic target of OP.

G protein-coupled receptor 91 activations suppressed mineralization in Porphyromonas gingivalis-infected osteoblasts.

Succinate receptor GPR91 is one of the G protein-coupled receptors (GPCRs) that interacts with various proteins to regulate diverse cellular functions such as cell morphology, apoptosis, and differentiation. In this study, we investigated whether the GPR91-mediated signaling pathway regulates mineralization in Porphyromonas gingivalis (P. gingivalis)-treated osteoblasts and to determine its potential role in osteoclast differentiation. Primary mouse osteoblasts from wild-type (WT) and GPR91 knockout (GPR91-/-) mice infected with P. gingivalis were used for in vitro experiments. The results showed that inhibition by 4C, a specific inhibitor, and GPR91 knockout promoted mineralization in P. gingivalis-infected osteoblasts. Surprisingly, GPR91 knockdown decreased the migration ability of osteoblasts. Moreover, compared with P. gingivalis-infected WT osteoblasts, GPR91-/- osteoblasts exhibited decreased RANKL production, and conditioned media (CM) from bacteria-infected GPR91-/- osteoblasts suppressed the formation of osteoclast precursors. Moreover, P. gingivalis mediated the role of GPR91 in osteoblast mineralization by activating the NF-κB pathway. These findings suggest that GPR91 activation reduces mineralization of P. gingivalis-infected osteoblasts and promotes osteoclastogenesis in macrophages. Therefore, targeting GPR91 may mitigate the loss of alveolar bone during bacterial infection.

Cell-microsphere based Living Microhybrids for Osteogenesis Regulating to Boosting Biomineralization

Abstract Biomineralization-based cell-material living composites ex vivo showed great potential for living materials construction and cell regulation. However, cells in scaffolds with unconnected pores usually induce confined nutrient transfer and cell-cell communications, affecting the transformation of osteoblasts into osteocytes and the mineralization process. Herein, the osteoblast-materials living hybrids were constructed with porous PLLA microspheres using a rational design, in which cell-based living materials presented an improved osteoblast differentiation and mineralization model using rationally designed cell-microsphere composites. The results indicated that the microfluidic-based technique provided an efficient and highly controllable approach for producing on-demand PLLA microspheres with tiny pores (< 5 μm), medium pores (5-15 μm), and large pores (> 15 μm), as well as further drug delivery. Furthermore, the simvastatin (SIM)-loaded porous PLLA microsphere with ε-polylysine (ε-PL) modification was used for osteoblast (MC3T3-E1) implantation, achieving the cell-material living microhybrids, and the results demonstrated the ε-PL surface modification and simvastatin could improve osteoblast behavior regulation, including cell adhesion, proliferation, as well as the antibacterial effects. Both in vitro and in vivo results significantly demonstrated further cell proliferation, differentiation, and cascade mineralization regulation. Then, the qPCR or histological staining of typical markers, including collagen type I (Col I), alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2) and bone morphogenetic protein 2 (BMP2), as well as the calcium mineral deposition staining in situ, reconfirmed the transformation of osteoblasts into osteocytes. These achievements revealed a promising boost in osteogenesis towards mineralization at the microtissue level by cell-microsphere integration, suggesting an alternative strategy for materials-based ex vivo tissue construction and cell regulation, further demonstrating excellent application prospects in the field of biomineralization-based tissue regeneration.

Investigating the Biological Efficacy of Albumin-Enriched Platelet-Rich Fibrin (Alb-PRF): A Study on Cytokine Dynamics and Osteoblast Behavior.

The development of effective biomaterials for tissue regeneration has led to the exploration of blood derivatives such as leucocyte- and platelet-rich fibrin (L-PRF). A novel variant, Albumin-Enriched Platelet-Rich Fibrin (Alb-PRF), has been introduced to improve structural stability and bioactivity, making it a promising candidate for bone regeneration. This study aimed to evaluate Alb-PRF's capacity for cytokine and growth factor release, along with its effects on the proliferation, differentiation, and mineralization of human osteoblasts in vitro. Alb-PRF membranes were analyzed using histological, scanning electron microscopy, and fluorescence microscopy techniques. Cytokine and growth factor release was quantified over seven days, and osteoinductive potential was evaluated with MG-63 osteoblast-like cells. Structural analysis showed Alb-PRF as a biphasic, highly cellularized material that releases lower levels of inflammatory cytokines and higher concentrations of platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) compared to L-PRF. Alb-PRF exhibited higher early alkaline phosphatase activity and in vitro mineralization (p < 0.05) and significantly increased the OPG/RANKL mRNA ratio (p < 0.05). These results indicate that Alb-PRF has promising potential as a scaffold for bone repair, warranting further in vivo and clinical assessments to confirm its suitability for clinical applications.

Measuring Calcium Levels in Bone-Resorbing Osteoclasts and Bone-Forming Osteoblasts.

Bone remodeling is a crucial, dynamic process that renews bone and maintains mineral homeostasis. It consists of several steps, including osteoclastic bone resorption and osteoblastic bone formation and mineralization. Intracellular calcium signaling is essential for osteoclast and osteoblast differentiation and activity. Here, we describe the differentiation of human osteoclasts and osteoblasts in vitro and provide common methods to determine cell differentiation and activity. We then describe protocols for measuringintracellular calcium in these cells using Fura2-AM.

Type-H endothelial cell protein Clec14a orchestrates osteoblast activity during trabecular bone formation and patterning

Type-H capillary endothelial cells control bone formation during embryogenesis and postnatal growth but few signalling mechanisms underpinning this influence have been characterised. Here, we identify a highly expressed type-H endothelial cell protein, Clec14a, and explore its role in coordinating osteoblast activity. Expression of Clec14a and its ligand, Mmrn2 are high in murine type-H endothelial cells but absent from osteoblasts. Clec14a−/− mice have premature condensation of the type-H vasculature and expanded distribution of osteoblasts and bone matrix, increased long-bone length and bone density indicative of accelerated skeletal development, and enhanced osteoblast maturation. Antibody-mediated blockade of the Clec14a-Mmrn2 interaction recapitulates the Clec14a−/− phenotype. Endothelial cell expression of Clec14a regulates osteoblast maturation and mineralisation activity during postnatal bone development in mice. This finding underscores the importance of type-H capillary control of osteoblast activity in bone formation and identifies a novel mechanism that mediates this vital cellular crosstalk.

Evaluation and Comparison of the Effect of Three Dental Luting Cements on Mineralized Bone Derived from Dental Pulp Stem Cells: An In Vitro Study.

Background and Objectives: This study aimed to investigate the effect of zinc phosphate (ZnP) cement, glass ionomer cement (GIC), and nano-integrated bio-ceramic (NIB) cement on mineralization when placed in contact with bone tissue-forming cells. Materials and Methods: ZnP cement, GIC, and NIB cement were divided into direct and indirect groups. A total of 72 cement pellets (24 pellets of each test sample) of 3 × 1 mm (width × height) were prepared using polytetrafluoroethylene molds. A total of 3 sample groups were demarcated using 96- cell well culture plates. In the control group, 24 wells were filled with mineralized osteoblasts and 1 µL of gingival crevicular fluid (GCF). In test group 1, to show a direct effect, 36 samples were plated with mineralized osteoblasts and 1 µL GCF for 24 h; the cells were directly exposed to cement pellets. A total of 36 samples were immersed in GCF for 24 h; later the supernatant was transferred to the mineralized osteoblasts to demonstrate an indirect effect in test group 2. To assess the mineralization, osteoblasts were stained with alizarin red and later observed under an inverted phase-contrast microscope. Data were analyzed using the statistical package for social sciences. An independent t-test compared the direct and indirect effects of the ZnP cement, GIC, NIB cement, and control groups on the mineralization of osteoblasts derived from hDPCs. Results: A statistically significant difference was observed between the ZnP cement, GIC, and NIB cement groups (p < 0.05). ZnP cement exhibited a moderate, NIB cement the least harmful effect, and GIC showed the most harmful effect on the mineralization of osteoblast cells. Conclusions: The biocompatibility of dental luting cements is an important aspect that clinicians should consider during their selection. Nano-integrated bio-ceramic cement showed the least negative effect on the mineralization of osteoblast cells which is beneficial for the cementation of cement-retained implant prostheses. However, further studies are needed to evaluate osteoblast and osteoclast activity in vivo.

A Surface-Mediated Biomimetic Porous Polyether-Ether-Ketone Scaffold for Regulating Immunity and Promoting Osteogenesis.

The repair of critical-sized bone defects remains a major challenge for clinical orthopedic surgery. Here, we develop a surface biofunctionalized three-dimensional (3D) porous polyether-ether-ketone (PEEK) scaffold that can simultaneously promote osteogenesis and regulate macrophage polarization. The scaffold is created using polydopamine (PDA)-assisted immobilization of silk fibroin (SF) and the electrostatic self-assembly of nanocrystalline hydroxyapatite (nano-HA) on a 3D-printed porous PEEK scaffold. The SF/nano-HA functionalized surface provides a bone-like microenvironment for osteoblastic cells' adhesion, proliferation, mineralization and osteogenic differentiation. Moreover, the biofunctionalized surface can effectively drive macrophages polarization from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype. Integrin β1-specific cell-matrix binding and the activation of Ca2+ receptor-mediated signaling pathway play critical roles in the regulation of macrophage polarization. Compared with the as-printed scaffold, the SF/nano-HA functionalized porous PEEK scaffold induces minimal inflammatory response, enhanced angiogenesis, and substantial new bone formation, resulting in improved osseointegration in vivo. This study not only develops a promising candidate for bone repair but also demonstrates a facile surface biofunctionalization strategy for orthopedic implants to improve osseointegration by stimulating osteogenesis and regulating immunity.

CD11B + CD36 + cells are bone anabolic macrophages that limit age-associated bone loss.

Disruptions in the bone remodeling cycle that occur with increasing age lead to degeneration of the skeleton and increased risk of fragility fractures. Our understanding of how the bone remodeling process within cortical bone is controlled and altered with age in males and females is limited. Here, we generated bone marrow chimeric mice to understand the impacts of age and sex on the bone remodeling process. We demonstrate that transplantation of aged male or female bone marrow into young lethally irradiated male hosts unexpectedly enhances cortical bone mass without an impacting cancellous bone. Our single cell RNA-sequencing data show that mice reconstituted with aged bone marrow exhibited subsets of cells marked by CD11B/CD36 expression that demonstrate enhanced production of anabolic cytokines as compared to young counterparts, and that these myeloid subsets exist under conditions of normal physiology in aged mice. Importantly, CD11B + CD36 + cells do not differentiate into osteoclasts in vitro, and CD36 does not mark TRAP+ cells in vivo. Instead, CD36 + cells localize to resorption sites, including within cortical bone defects, suggesting their involvement in cortical bone remodeling and healing. CD11B + CD36 + cells also express elevated levels of bone anabolic WNT ligands, especially Wnt6. In functional assays, we demonstrate that soluble factors produced by CD11B + CD36 + cells enhance osteoblast progenitor commitment, mineralization, and activation of WNT signaling in vitro. Moreover, CD11B/CD36 exquisitely mark a subset of anabolic myeloid cells within human bone marrow. In conclusion, our studies identified a novel population of aged macrophages that limit cortical bone loss.

Relaxin-2 promotes osteoblastic differentiation mediated by epidermal growth factor and epidermal growth factor receptor signaling.

Loss of osteogenic differentiation potential of osteoblasts has been associated with the pathogenesis of osteoporosis. Thus, stimulation of osteoblastic differentiation is a therapeutic strategy for osteoporosis. Relaxin-2 is a peptide hormone with potent biological functions. However, the effects of Relaxin-2 in osteoblastic differentiation and osteoporosis have not been reported before. Here, we report a novel physiological role of Relaxin-2 in promoting osteoblastic differentiation and mineralization of MC3T3-E1 cells. Our results indicate that exposure to Relaxin-2 upregulated the expression, and elevated the activity of alkaline phosphatase (ALP) when MC3T3-E1 cells were cultured in osteogenic differentiation medium (OM). Additionally, Relaxin-2 upregulated the mRNA levels of osteocalcin (ocn), osteopontin (opn), and collagen type I alpha 1 (Col1a1). The alizarin red S staining assay revealed that Relaxin-2 promoted the mineralization of MC3T3-E1 cells. We also found that Relaxin-2 increased the expression of Runx-2 as well as the epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR). Importantly, silencing of EGF abolished the effects of Relaxin-2 in osteoblastic differentiation and related gene expression. These findings suggest that Relaxin-2 stimulates osteogenic differentiation through activating EGF/EGFR signaling.

LMK-235 suppresses osteoclastogenesis and promotes osteoblastogenesis by inhibiting HDAC4

Osteoblasts and osteoclasts play an important role in maintaining the structural integrity of bone tissue, in which osteoclasts degrade bone structure and osteoblasts restore bone tissue. The imbalance of osteoblast and osteoclast function can lead to many bone-related diseases, such as osteoporosis and inflammatory osteolysis. The drug that can both promote bone formation and inhibit bone loss will be able to treat those diseases. In this study, it was found that LMK-235, an selective HDAC4/5 inhibitor, inhibited the differentiation and maturation of osteoclasts by regulating NF-κB and p-Smad2/3 signaling pathways via inhibition of HDAC4. At the same time, we found that LMK-235 promoted osteoblast mineralization by upregulating Runx2 expression via inhibition of HDAC4. In vivo, LMK-235 was able to alleviate lipopolysaccharide (LPS)-induced calvarial osteolysis and promote the repair of bone defects. Taken together, LMK-235 suppresses osteoclast differentiation and promotes osteoblast formation by inhibiting HDAC4. This may provide a valuable treatment for bone diseases caused by abnormal osteoclast bone resorption and osteoblast bone regeneration.

Pro-differentiative, Pro-adhesive and Pro-migratory Activities of Isorhamnetin in MC3T3-E1 Osteoblasts via Activation of ERK-dependent BMP2-Smad Signaling.

Osteoporosis (OP) is an epidemic bone remodeling disorder of growing relevance with the aging population. Considering that isorhamnetin (ISO), a flavonoid derived from plant, has been newly reckoned as an active ingredient in treating OP, our paper was conducted to investigate the regulatory role and mechanism of ISO in OP. CCK-8 method detected cell activity. Alkaline phosphatase (ALP) assay kit, ALP staining and alizarin red S staining measured osteogenic differentiation. RT-qPCR and Western blot examined the expressions of osteoblast-related proteins. Wound healing and cell adhesion assays severally detected cell migration and adhesion. Also, Western blot tested the expressions of extracellular signal-regulated kinase (ERK) signaling-associated proteins. As illustrated, after MC3T3-E1 pre-osteoblasts were stimulated to differentiate to osteoblasts, ISO markedly promoted the differentiation, mineralization, migration and adhesion of MC3T3-E1 osteoblasts in a concentration-dependent manner. In addition, administration of ISO functioned as an activator of ERK-dependent BMP2-Smad signaling in MC3T3-E1 osteoblasts and pretreatment with ERK inhibitor PD98059 partially compensated the impacts of ISO on MC3T3-E1 osteoblasts differentiation, mineralization, migration as well as adhesion. To be summarized, ISO might activate ERK-dependent BMP2-Smad signaling to facilitate the differentiation, mineralization, migration and adhesion of MC3T3-E1 osteoblasts, suggesting the protective potential of ISO in OP.

Pharmacological impacts of tanshinone on osteogenesis and osteoclastogenesis: a review.

Tanshinone, a lipophilic component of Salvia miltiorrhiza, is used to treat diseases like atherosclerosis, hypertension, Alzheimer's disease, and diabetes mellitus through its pharmacological activities like anti-inflammatory, anti-oxidant, and anti-tumor. Excessive inflammation is the primary cause of bone diseases such as osteoporosis and rheumatoid arthritis, affecting more than millions of people across the globe. Recently, tanshinone has shown potential benefits against bone diseases by modulating signaling pathways accountable for the proliferation and differentiation of bone cells. In vitro and in vivo studies reported that tanshinone promotes osteoblast formation and mineralization and suppresses excessive bone resorption during disease conditions. In this review, we have summarized the beneficial effects of tanshinone and other extracts of Salvia miltiorrhiza for bone health and their potential molecular targets in signaling.

Heraclenin promotes the osteogenic differentiation of bone marrow stromal cells by activating the RhoA/ROCK pathway.

Osteoporosis is a devastating skeletal disease, the pathogenesis of which is related to abnormal bone metabolism, featured by the imbalance between osteoblastic bone formation and osteoclastic bone resorption. Stem cell-based therapies have been demonstrated to improve osteoporosis treatment. Previously, the linear furanocoumarin heraclenin was reported to enhance osteoblast differentiation and mineralization in mouse mesenchymal stem cells (MSCs), suggesting its potential for osteogenic differentiation and bone regeneration. Our study was designed to confirm the promotive role of heraclenin on osteogenic differentiation of human bone MSCs (BMSCs) and explore the underlying mechanisms. Human BMSCs were treated for 24, 48, and 72h with heraclenin (5, 10, 20, 40, and 80 μM), and cell viability was determined by Cell Counting Kit-8 (CCK-8) assay. To further evaluate the cytotoxicity of heraclenin, cell suspension obtained from BMSCs treated with heraclenin (5, 10, and 20 μM) for 72h was subjected to a MUSE™ cell analyzer for cell viability and count assay. BMSCs were incubated in osteogenic induction medium for 7 days. Then, osteogenic differentiation and mineralization of BMSCs were assessed through alkaline phosphatase (ALP) and Alizarin Red S staining. The expression of osteogenesis markers including ALP, osteocalcin (OCN), osterix (OSX), and runt-related transcription factor 2 (RUNX2) was detected via reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blotting. The effects of heraclenin on the RhoA/ROCK pathway were estimated through western blotting. Y-27632, the ROCK inhibitor, was used to confirm the role of the RhoA/ROCK pathway in heraclenin-mediated osteogenic differentiation of BMSCs. Heraclenin (5-80 μM) was non-toxic on human BMSCs. Heraclenin treatment (5-20 μM) dose-dependently enhanced ALP activity and calcium deposition. Furthermore, heraclenin promoted ALP, OCN, OSX, and RUNX2 mRNA and protein expression. Mechanically, heraclenin treatment increased RhoA and ROCK1 mRNA expression, stimulated the translocation of ROCK from the cytosolic to the membrane fraction, and elevated the protein levels of phosphorylated cofilin (p-cofilin) and active RhoA. Additionally, treatment with Y-27632 overturned the promotion of heraclenin on ALP activity, calcium deposition, the expression of osteogenesis markers, and the RhoA/ROCK signaling pathway. Heraclenin facilitates the osteogenic differentiation of human BMSCs through the activation of the RhoA/ROCK pathway.

Expression of Kielin/chordin-like protein is regulated by BMP-2 in osteoblasts

Bone morphogenetic protein (BMP), an osteoinductive factor, is a cytokine that induces osteoblast differentiation and mineralization, and expected to be applicable for hard tissue reconstruction. Kielin/chordin-like protein (Kcp), a member of the family of cysteine-rich proteins, enhances BMP signaling. The present study found that expression of Kcp in osteoblasts was induced by BMP-2 in a concentration- and time-dependent manner. Up-regulation of Kcp by BMP-2 was inhibited by Dorsomorphin, a SMAD signaling inhibitor. The involvement of up-regulation of Kcp by BMP-2 in induction of osteoblast differentiation by BMP-2 was also examined, which showed that suppression of Kcp expression by si Kcp partially inhibited induction of osteoblast differentiation and mineralization by BMP-2. Together, these results suggest that Kcp induced by BMP-2 functions to provide positive feedback for promotion of osteoblastic differentiation and mineralization by BMP-2 in osteoblasts.

Mechanical Properties, Drug Release, Biocompatibility, and Antibacterial Activities of Modified Emulsified Gelatin Microsphere Loaded with Gentamicin Composite Calcium Phosphate Bone Cement In Vitro.

Bone defects are commonly addressed with bone graft substitutes; however, surgical procedures, particularly for open and complex fractures, may pose a risk of infection. As such, a course of antibiotics combined with a drug carrier is often administered to mitigate potential exacerbations. This study involved the preparation and modification of emulsified (Em) crosslinking-gelatin (gel) microspheres (m-Em) to reduce their toxicity. The antibiotic gentamicin was impregnated into gel microspheres (m-EmG), which were incorporated into calcium phosphate bone cement (CPC). The study investigated the effects of m-EmG@CPC on antibacterial activity, mechanical properties, biocompatibility, and proliferation and mineralization of mouse progenitor osteoblasts (D1 cells). The average size of the gel microspheres ranged from 22.5 to 16.1 μm, with no significant difference between the groups (p > 0.05). Most of the oil content within the microspheres was transferred through modification, resulting in reduced cytotoxicity. Furthermore, antibiotic-impregnated m-EmG did not compromise the intrinsic properties of the microspheres and exhibited remarkably antibacterial effects. After combining with CPC (m-EmG@CPC), the microspheres did not significantly hinder the CPC reaction and produced the main product, hydroxyapatite (HA). However, the compressive strength of the largest microsphere content of 0.5 wt.% m-EmG in CPC decreased significantly from 59.8 MPa of CPC alone to 38.7 MPa of 0.5m-EmG@CPC (p < 0.05). The 0.5m-EmG@CPC composite was effective against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in drug release and antibacterial tests. Compared with m-EmG alone, the 0.5m-EmG@CPC composite showed no toxicity to mouse fibroblast cells (L929). Additionally, the proliferation and mineralization of mouse osteoblastic osteoprogenitor cells (D1 cells) did not have a negative impact on the 0.5m-EmG@CPC composite over time in culture compared with CPC alone. Results suggest that the newly developed antibacterial 0.5m-EmG@CPC composite bone cement did not negatively affect the performance of osteoprogenitor cells and could be a new option for bone graft replacement in surgeries.

Humidity-Responsive Amorphous Calcium-Magnesium Pyrophosphate/Cassava Starch Scaffold for Enhanced Neurovascular Bone Regeneration.

Developing a neurovascular bone repair scaffold with an appropriate mechanical strength remains a challenge. Calcium phosphate (CaP) is similar to human bone, but its scaffolds are inherently brittle and inactive, which require recombination with active ions and polymers for bioactivity and suitable strength. This work discussed the synthesis of amorphous magnesium-calcium pyrophosphate (AMCP) and the subsequent development of a humidity-responsive AMCP/cassava starch (CS) scaffold. The scaffold demonstrated enhanced mechanical properties by strengthening the intermolecular hydrogen bonds and ionic bonds between AMCP and CS during the gelatinization and freeze-thawing processes. The release of active ions was rapid initially and stabilized into a long-term stable release after 3 days, which is well-matched with new bone growth. The release of pyrophosphate ions endowed the scaffold with antibacterial properties. At the cellular level, the released active ions simultaneously promoted the proliferation and mineralization of osteoblasts, the proliferation and migration of endothelial cells, and the proliferation of Schwann cells. At the animal level, the scaffold was demonstrated to promote vascular growth and peripheral nerve regeneration in a rat skull defect experiment, ultimately resulting in the significant and rapid repair of bone defects. The construction of the AMCP/CS scaffold offers practical suggestions and references for neurovascular bone repair.

Collagen structures of demineralized bone paper direct mineral metabolism.

Bone is a dynamic mineralized tissue that undergoes continuous turnover throughout life. While the general mechanism of bone mineral metabolism is documented, the role of underlying collagen structures in regulating osteoblastic mineral deposition and osteoclastic mineral resorption remains an active research area, partly due to the lack of biomaterial platforms supporting accurate and analytical investigation. The recently introduced osteoid-inspired demineralized bone paper (DBP), prepared by 20-μm thin sectioning of demineralized bovine compact bone, holds promise in addressing this challenge as it preserves the intrinsic bony collagen structure and retains semi-transparency. Here, we report on the impact of collagen structures on modulating osteoblast and osteoclast-driven bone mineral metabolism using vertical and transversal DBPs that exhibit a uniaxially aligned and a concentric ring collagen structure, respectively. Translucent DBP reveals these collagen structures and facilitates longitudinal tracking of mineral deposition and resorption under brightfield microscopy for at least 3wk. Genetically labeled primary osteogenic cells allow fluorescent monitoring of these cellular processes. Osteoblasts adhere and proliferate following the underlying collagen structures of DBPs. Osteoblastic mineral deposition is significantly higher in vertical DBP than in transversal DBP. Spatiotemporal analysis reveals notably more osteoblast adhesion and faster mineral deposition in vascular regions than in bone regions. Subsequent osteoclastic resorption follows these mineralized collagen structures, directing distinct trench and pit-type resorption patterns. In vertical DBP, trench-type resorption occurs at an 80% frequency, whereas transversal DBP shows 35% trench-type and 65% pit-type resorption. Our studies substantiate the importance of collagen structures in regulating mineral metabolism by osteogenic cells. DBP is expected to serve as an enabling biomaterial platform for studying various aspects of cellular and extracellular bone remodeling biology.

Hydroxyapatite-whitlockite composite coating as a biomimetic material for bone integration

Mg deficiency contributes to disrupting mineral metabolism and impairing bone growth. Continuous supply of Mg2+ from orthopedic implant has emerged as a therapeutic strategy for fracture healing. However, therapeutic efficiency of Mg2+ is concentration-dependent and the controlled Mg2+ delivery is challenging. Mg whitlockite (WH) is Mg2+ reservoir in bone mineral which manipulates Mg2+ release and enhances mechanical strength of natural bone. In this aspect, WH was incorporated into the hydroxyapatite (HAp) coating to endow the coating with Mg2+-release properties and enhance bonding strength to the metal substrate. The HAp/WH composite coating with 30 wt% WH exhibited a two-fold increase in bonding strength than the HAp coating mainly due to the better thermal adaptation of WH to the Ti substrate. The Mg2+-concentration-dependent osteoblastic behaviors were evaluated by using the WH, annealed-treated WH (WH-800) and HAp/WH composite coatings. Compared to HAp and WH-800 coatings, WH and HAp/WH coatings with higher Mg2+ release (4.1–11.5 mM within 7 days) and more negative zeta potential (−36.5 mV and −27.3 mV) exerted greater effects on fibronectin adsorption and unfolding the exposure of RGD motif which facilitated cytoskeleton spreading and enhanced osteoblastic differentiation and mineralization. Considering the difference in Mg2+ release among the WH-containing coatings, our study suggested that 3–12 mM Mg2+in vitro may be optimized. Taken together, the first-time reported HAp/WH composite coating as a biomimetic material shows promise in enhancing bone integration.

NP-12 peptide functionalized nanoparticles counteract the effect of bacterial lipopolysaccharide on cultured osteoblasts

ObjectiveTo evaluate whether nanoparticles (NPs) functionalized with Tideglusib (TDg, NP-12), and deposited on titanium surfaces, would counteract the effect of bacterial lipopolysaccharide (LPS) on osteoblasts. MethodsExperimental groups were: (a) Titanium discs (TiD), (b) TiD covered with undoped NPs (Un-NPs) and (c) TiD covered with TDg-doped NPs (TDg-NPs). Human primary osteoblasts were cultured onto these discs, in the presence or absence of bacterial LPS. Cell proliferation was assessed by MTT-assay and differentiation by measuring the alkaline phosphatase activity. Mineral nodule formation was assessed by the alizarin red test. Real-time quantitative polymerase chain reaction was used to study the expression of Runx-2, OSX, ALP, OSC, OPG, RANKL, Col-I, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF-βR2, and TGF-βR3 genes. Osteoblasts morphology was studied by Scanning Electron Microscopy. One-way ANOVA or Kruskal-Wallis and Bonferroni multiple comparisons tests were carried out (p < 0.05). ResultsTDg-NPs enhanced osteoblasts proliferation. Similarly, this group increased ALP production and mineral nodules formation. TDg-NPs on titanium discs resulted in overexpression of the proliferative genes, OSC and OSX, regardless of LPS activity. In the absence of LPS, TDg-NPs up-regulated Runx2, COL-I, ALP, BMP2 and BMP7 genes. OPG/RANKL gene ratios were increased about 2500 and 4,000-fold by TDg-NPs, when LPS was added or not, respectively. In contact with the TDg-NPs osteoblasts demonstrated an elongated spindle-shaped morphology with extracellular matrix production. SignificanceTDg-NPs on titanium discs counteracted the detrimental effect of LPS by preventing the decrease on osteoblasts proliferation and mineralization, and produced an overexpression of proliferative and bone-promoting genes on human primary osteoblasts.