Magnesium Chloride promotes Osteogenesis through Notch signaling activation and expansion of Mesenchymal Stem Cells

Bioceramic-mediated chondrocyte hypertrophy promotes calcified cartilage formation for rabbit osteochondral defect repair

Osteochondral tissue is a highly specialized and complex tissue composed of articular cartilage and subchondral bone that are separated by a calcified cartilage interface. Multilayered or gradient scaffolds, often in conjunction with stem cells and growth factors, have been developed to mimic the respective layers for osteochondral defect repair. In this study, we designed a hyaline cartilage-hypertrophic cartilage bilayer graft (RGD/RGDW) with chondrocytes. Previously, we demonstrated that RGD peptide-modified chondroitin sulfate cryogel (RGD group) is chondro-conductive and capable of hyaline cartilage formation. Here, we incorporated whitlockite (WH), a Mg2+-containing calcium phosphate, into RGD cryogel (RGDW group) to induce chondrocyte hypertrophy and form collagen X-rich hypertrophic cartilage. This is the first study to use WH to produce hypertrophic cartilage. Chondrocytes-laden RGDW cryogel exhibited significantly upregulated expression of hypertrophy markers in vitro and formed ectopic hypertrophic cartilage in vivo, which mineralized into calcified cartilage in bone microenvironment. Subsequently, RGD cryogel and RGDW cryogel were combined into bilayer (RGD/RGDW group) and implanted into rabbit osteochondral defect, where RGD layer supports hyaline cartilage regeneration and bioceramic-containing RGDW layer promotes calcified cartilage formation. While the RGD group (monolayer) formed hyaline-like neotissue that extends into the subchondral bone, the RGD/RGDW group (bilayer) regenerated hyaline cartilage tissue confined to its respective layer and promoted osseointegration for integrative defect repair.

Treatment of osteoarthritis by implantation of Mg- and WE43-cylinders - A preclinical study on bone and cartilage changes and their influence on pain sensation in rabbits

With its main features of cartilage degeneration, subchondral bone sclerosis and osteophyte formation, osteoarthritis represents a multifactorial disease with no effective treatment options. As biomechanical shift in the trabecular network may be a driver for further cartilage degeneration, bone enhancement could possibly delay OA progression. Magnesium is known to be osteoconductive and already showed positive effects in OA models. We aimed to use magnesium cylinders to enhance subchondral bone quality, condition of cartilage and pain sensation compared to sole drilling in vivo. After eight weeks of implantation in rabbits, significant increase in subchondral bone volume and trabecular thickness with constant bone mineral density was found indicating favored biomechanics. As representative for pain, a higher number of CD271+ vessels were present in control samples without magnesium. However, this result could not be confirmed by sensitive, objective lameness evaluation using a pressure sensing mat and no positive effect could be shown on either cartilage degeneration evaluated by OARSI score nor the presence of regenerative cells in CD271-stained samples. The presented results show a relevant impact of implanted magnesium on key structures in OA pain with missing clinical relevance regarding pain. Further studies with shifted focus should examine additional structures as joint capsule or osteophytes.

Construction of a Titanium-Magnesium Composite Internal Fixation System for Repairing Bone Defects

The repair and regeneration of maxillofacial bone defects are major clinical challenges. Titanium (Ti)-magnesium (Mg) composites are a new generation of revolutionary internal fixation materials encompassing the mechanical strength and bioactive advantages of Ti and Mg alloys, respectively. This study was aimed to construct a Ti-Mg composite internal plate/screw fixation system to fix and repair bone defects. Further, the effects of different internal fixation systems on bone repair were analyzed through radiological and histological analyses. Notably, Ti6Al4V with rolled Mg foil was used as the experimental group, and a bone defect model of transverse complete amputation of the ulna in rabbits similar to the clinical condition was established. The internal fixation system with the highest osteogenic efficiency was selected based on in vivo results, and the direct and indirect bone repair abilities of the selected materials were evaluated in vitro. Notably, the thin Mg foil-Ti6Al4V internal fixation system exhibited the best fixation effect in the bone defect model and promoted the formation of new bone and early healing of bone defect areas. In vitro, the thin Mg foil-Ti6Al4V composite enhanced the activity of MC3T3-E1 cells; promoted the proliferation, adhesion, extension, and osteogenic differentiation of MC3T3-E1 cells; and regulated new bone formation. Further, it also promoted the polarization of RAW264.7 cells to M2 macrophages, induced the osteogenic immune microenvironment, and indirectly regulated the bone repair process. Therefore, a internal fixation system holds a promising potential for the internal fixation of maxillofacial bone defects. Our findings provide a theoretical and scientific basis for the design and clinical application of Ti-Mg internal fixation systems.

Impact of Strontium, Magnesium, and Zinc Ions on the In Vitro Osteogenesis of Maxillary Sinus Membrane Stem Cells

Human Maxillary Sinus Membrane Stem Cells (hMSMSCs) contribute significantly to bone formation following maxillary sinus floor augmentation (MSFA). The biological behavior of mesenchymal stem cells is notably influenced by varying concentrations of magnesium (Mg2+), strontium (Sr2+), and zinc (Zn2+) ions; however, their specific effects on hMSMSCs have not been comprehensively studied. We isolated hMSMSCs and identified their mesenchymal stem cell characteristics by flow cytometry and multilineage differentiation experiments. Subsequently, the hMSMSCs were cultured in media containing different concentrations of these metal ions. The proliferation and viability of hMSMSCs were assessed using CCK-8 and Calcein AM/PI staining. After osteogenic induction, cells were evaluated for alkaline phosphatase (ALP) activity, ALP staining, and Alizarin Red staining. Additionally, qRT-PCR was used to detect differences in osteogenic gene expression, and immunofluorescence staining was used to observe variations in OCN protein levels. The results indicated that 1 mM Mg2+, 0.01 mM Sr2+, and 0.001 mM Zn2+ significantly improved the proliferation and activity of hMSMSCs. These concentrations also notably enhanced ALP secretion, increased bone-related gene expression, and augmented osteocalcin expression and formation of extracellular calcium nodules, thereby improving osteogenic differentiation. However, higher concentrations of Mg2+, Sr2+, and Zn2+ decreased cell viability and osteogenic differentiation. Mg2+, Sr2+, and Zn2+ promote osteogenic differentiation and proliferation of hMSMSCs in a concentration-dependent manner, indicating that the type and concentration of ions in the extracellular environment can significantly alter hMSMSCs behavior, which is a crucial consideration for material design in maxillary sinus elevation applications.

Establishment of porcine embryonic stem cells in simplified serum free media and feeder free expansion

BACKGROUND

The establishment of stable porcine embryonic stem cells (pESCs) can contribute to basic and biomedical research, including comparative developmental biology, as well as assessing the safety of stem cell-based therapies. Despite these advantages, most pESCs obtained from in vitro blastocysts require complex media and feeder layers, making routine use, genetic modification, and differentiation into specific cell types difficult. We aimed to establish pESCs with a single cell-passage ability, high proliferative potency, and stable in long-term culture from in vitro-derived blastocysts using a simplified serum-free medium.

METHODS

We evaluated the establishment efficiency of pESCs from in vitro blastocysts using various basal media (DMEM/F10 (1:1), DMEM/F12, and a-MEM) and factors (FGF2, IWR-1, CHIR99021, and WH-4-023). The pluripotency and self-renewal capacity of the established pESCs were analyzed under feeder or feeder-free conditions. Ultimately, we developed a simplified culture medium (FIW) composed of FGF2, IWR-1, and WH-4-023 under serum-free conditions.

RESULTS

The pESC-FIW lines were capable of single-cell passaging with short cell doubling times and expressed the pluripotency markers POU5F1, SOX2, and NANOG, as well as cell surface markers SSEA1, SSEA4, and TRA-1-60. pESC-FIW showed a stable proliferation rate and normal karyotype, even after 50 passages. Transcriptome analysis revealed that pESC-FIW were similar to reported pESC maintained in complex media and showed gastrulating epiblast cell characteristics. pESC-FIW were maintained for multiple passages under feeder-free conditions on fibronectin-coated plates using mTeSR™, a commercial medium used for feeder-free culture, exhibiting characteristics similar to those observed under feeder conditions.

CONCLUSIONS

These results indicated that inhibition of WNT and SRC was sufficient to establish pESCs capable of single-cell passaging and feeder-free expansion under serum-free conditions. The easy maintenance of pESCs facilitates their application in gene editing technology for agriculture and biomedicine, as well as lineage commitment studies.

Multifunctional Sr,Mg-Doped Mesoporous Bioactive Glass Nanoparticles for Simultaneous Bone Regeneration and Drug Delivery

Mesoporous bioactive glass nanoparticles (MBGNs) doped with therapeutical ions present multifunctional systems that enable a synergistic outcome through the dual delivery of drugs and ions. The aim of this study was to evaluate influence of co-doping with strontium and magnesium ions (SrMg-MBGNs) on the properties of MBGNs. A modified microemulsion-assisted sol-gel synthesis was used to obtain particles, and their physicochemical properties, bioactivity, and drug-loading/release ability were evaluated. Indirect biological assays using 2D and 3D cell culture models on human bone marrow-derived mesenchymal stem cells (hBM-MSCs) and endothelial EA.hy926 cells, respectively, were used to determine biocompatibility of MBGNs, their influence on alkaline phosphatase (ALP) production, calcium deposition, and cytoskeletal organization. Results showed that Sr,Mg-doping increased pore volume and solubility, and changed the mesoporous structure from worm-like to radial-dendritic, which led to a slightly accelerated drug release compared to pristine MBGNs. Biological assays confirmed that particles are biocompatible, and have ability to slightly induce ALP production and calcium deposition of hBM-MSCs, as well as to significantly improve the proliferation of EA.hy926 compared to biochemical stimulation via vascular endothelial growth factor (VEGF) administration or regular media. Fluorescence staining revealed that SrMg-MBGNs had a similar effect on EA.hy926 cytoskeletal organization to the VEGF group. In conclusion, Sr,Mg-MBGNs might be considered promising biomaterial for biomedical applications.

In vitro and in vivo evaluation of osteogenesis and antibacterial activity of MgGa alloys

MgGa alloys are considered highly potential biodegradable materials, owing to its good mechanical properties and appropriate corrosion resistance. However, it is still far from application due to the lack of biological evaluation. In the present study, biocompatibility, osteogenesis and antibacterial activity of extruded Mg-xGa (x = 1 and 5 wt%) alloys were investigated by in vitro cell culture experiments and in vivo implantation. The cell adhesion and proliferation of osteoblast precursor cells (MC3T3-E1) showed the excellent cytocompatibility of Mg-1Ga and poor cytocompatibility of Mg-5Ga. The osteogenic activity was evaluated and revealed that Ga3+ in the Mg-1Ga extract had the ability to enhance osteogenic differentiation through the facilitation of its early stages. In vivo studies in a rat femoral condyle model revealed that both Mg-1Ga and Mg-5Ga significantly promoted new bone formation without causing any adverse effects. Mg-5Ga exhibited a much higher corrosion rate in vivo than Mg-1Ga. Its osteogenic activity was better due to the rapid release of Mg2+ and Ga3+, but this caused premature structural integrity loss. Mg-1Ga and Mg-5Ga released Ga3+ to inhibit E. coli and S. aureus, with antibacterial rate increasing with Ga content. Our studies demonstrate that Mg-Ga alloys have the potential to be used as osteogenic and antibacterial implant materials. STATEMENT OF SIGNIFICANCE: This study evaluates the biocompatibility, osteogenesis, and antibacterial activity of Mg-Ga alloys, which are promising biodegradable materials for medical applications. The study finds that Mg-1Ga exhibits excellent cytocompatibility and promotes osteogenic differentiation, facilitating the early stages of osteoblast precursor cell development. In vivo studies in a rat femoral condyle model reveal that Mg-1Ga and Mg-5Ga significantly promote new bone formation without causing any adverse effects. The antibacterial activity of both alloys is evaluated against E. coli and S. aureus, with the inhibition rate increasing with Ga content. These findings suggest that Mg-Ga alloys have the potential to serve as osteogenic and antibacterial implant materials, providing significant insights into the development of novel biomedical implants.

Mg-Cross-Linked Alginate Hydrogel Induces BMSC/Macrophage Crosstalk to Enhance Bone Tissue Regeneration via Dual Promotion of the Ligand-Receptor Pairing of the OSM/miR-370-3p-gp130 Signaling Pathway

Macrophages play a pivotal role in the crosstalk between the immune and skeletal systems, while Mg-based biomaterials demonstrate immunomodulatory capabilities in this procedure. However, the mechanism of how Mg2+ promotes osteogenesis through the interplay of bone marrow-derived mesenchymal stem cells (BMSCs) and macrophages remains undescribed. Here, we demonstrated that a Mg-cross-linked alginate hydrogel exerted a dual enhancement of BMSCs osteogenic differentiation through the ligand-receptor pairing of the OSM/miR-370-3p-gp130 axis. On the one hand, Mg2+, released from the Mg-cross-linked hydrogel, stimulates bone marrow-derived macrophages to produce and secrete more OSM. On the other hand, Mg2+ lowers the miR-370-3p level in BMSCs and in turn, reverses its suppression on gp130. Then, the OSM binds to the gp130 heterodimer receptor and activates intracellular osteogenic programs in BMSCs. Taken together, this study reveals a novel cross-talk pattern between the skeletal and immune systems under Mg2+ stimulation. This study not only brings new insights into the immunomodulatory properties of Mg-based biomaterials for orthopedic applications but also enriches the miRNA regulatory network and provides a promising target to facilitate bone regeneration in large bone defects.

Application and Perspectives: Magnesium Materials in Bone Regeneration

The field of bone regeneration has always been a hot and difficult research area, and there is no perfect strategy at present. As a new type of biodegradable material, magnesium alloys have excellent mechanical properties and bone promoting ability. Compared with other inert metals, magnesium alloys have significant advantages and broad application prospects in the field of bone regeneration. By searching the official Web sites and databases of various funds, this paper summarizes the research status of magnesium composites in the field of bone regeneration and introduces the latest scientific research achievements and clinical transformations of scholars in various countries and regions, such as improving the corrosion resistance of magnesium alloys by adding coatings. Finally, this paper points out the current problems and challenges, aiming to provide ideas and help for the development of new strategies for the treatment of bone defects and fractures.

Novel artificial tricalcium phosphate and magnesium composite graft facilitates angiogenesis in bone healing

BACKGROUND

Bone grafting is the standard treatment for critical bone defects, but autologous grafts have limitations like donor site morbidity and limited availability, while commercial artificial grafts may have poor integration with surrounding bone tissue, leading to delayed healing. Magnesium deficiency negatively impacts angiogenesis and bone repair. Therefore, incorporating magnesium into a synthetic biomaterial could provide an excellent bone substitute. This study aims to evaluate the morphological, mechanical, and biological properties of a calcium phosphate cement (CPC) sponge composed of tetracalcium phosphate (TTCP) and monocalcium phosphate monohydrate (MCPM), which could serve as an excellent bone substitute by incorporating magnesium.

METHODS

This study aims to develop biomedical materials composed mainly of TTCP and MCPM powder, magnesium powder, and collagen. The materials were prepared using a wet-stirred mill and freeze-dryer methods. The particle size, composition, and microstructure of the materials were investigated. Finally, the biological properties of these materials, including 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay for biocompatibility, effects on bone cell differentiation by alkaline phosphatase (ALP) activity assay and tartrate-resistant acid phosphatase (TRAP) activity assay, and endothelial cell tube formation assay for angiogenesis, were evaluated as well.

RESULTS

The data showed that the sub-micron CPC powder, composed of TTCP/MCPM in a 3.5:1 ratio, had a setting time shorter than 15 minutes and a compressive strength of 4.39±0.96 MPa. This reveals that the sub-micron CPC powder had an adequate setting time and mechanical strength. We found that the sub-micron CPC sponge containing magnesium had better biocompatibility, including increased proliferation and osteogenic induction effects without cytotoxicity. The CPC sponge containing magnesium also promoted angiogenesis.

CONCLUSION

In summary, we introduced a novel CPC sponge, which had a similar property to human bone promoted the biological functions of bone cells, and could serve as a promising material used in bone regeneration for critical bone defects.

Silk Fibroin-Laponite Porous Microspheres as Cell Microcarriers for Osteogenic Differentiation

Silk fibroin (SF) has garnered significant attention as a natural polymer for fabricating porous scaffolds in various engineering applications. However, the limited osteoinductive property of SF has hindered its efficacy in bone repair applications. In this study, we constructed an SF-based injectable porous microcarrier that is doped with laponite (LAP), containing magnesium ions (Mg2+). The influence of freezing temperatures and concentrations of SF and LAP on the structural parameters of SF-LAP microcarriers was investigated. The SF-LAP microcarrier exhibited a porosity of 76.7 ± 1.2% and a controlled pore size of 24.6 ± 4.0 μm. At the 6 weeks of in vitro degradation test, a mild alkaline level in culture medium containing SF-LAP microcarriers was detected. The release of Mg2+ from the SF-LAP microcarrier was maintained at a concentration within the range of 1.2-2.3 mM during the 6 weeks. The seeded human adipose-derived stem cells in the SF-LAP microcarrier demonstrated a significant enhancement in osteogenic differentiation compared with cells seeded in the pure SF microcarrier, as evidenced by quantitative alkaline phosphatase activity and the expression of osteogenic marker genes. These findings underscore the potential of the SF-LAP microcarrier as an ideal cell carrier in the treatment of bone defects.

Advances in magnesium-containing bioceramics for bone repair

Reconstruction of bone defects or fractures caused by ageing, trauma and tumour resection is still a great challenge in clinical treatment. Although autologous bone graft is considered as gold standard, the source of natural bone is limited. In recent years, regenerative therapy based on bioactive materials has been proposed for bone reconstruction. Specially, numerous studies have indicated that bioactive ceramics including silicate and phosphate bioceramics exhibit excellent osteoinductivity and osteoconductivity, further promote bone regeneration. In addition, magnesium (Mg) element, as an indispensable mineral element, plays a vital role in promoting bone mineralisation and formation. In this review, different types of Mg-containing bioceramics including Mg-containing calcium phosphate-based bioceramics (such as Mg-hydroxyapatite, Mg-biphasic calcium phosphate), Mg-containing calcium silicate-based bioceramics (such as Mg2SiO4, Ca2MgSi2O7 and Mg-doped bioglass), Mg-based biocements, Mg-containing metal/polymer-bioceramic composites were systematacially summarised. Additionally, the fabrication technologies and their materiobiological effects were deeply discussed. Clinical applications and perspectives of magnesium-containing bioceramics for bone repair are highlighted. Overall, Mg-containing bioceramics are regarded as regenerative therapy with their optimised performance. Furthermore, more in-depth two-way researches on their performance and structure are essential to satisfy their clinical needs.

Bioabsorbable Composites Based on Polymeric Matrix (PLA and PCL) Reinforced with Magnesium (Mg) for Use in Bone Regeneration Therapy: Physicochemical Properties and Biological Evaluation

Improvements in Tissue Engineering and Regenerative Medicine (TERM)-type technologies have allowed the development of specific materials that, together with a better understanding of bone tissue structure, have provided new pathways to obtain biomaterials for bone tissue regeneration. In this manuscript, bioabsorbable materials are presented as emerging materials in tissue engineering therapies related to bone lesions because of their ability to degrade in physiological environments while the regeneration process is completed. This comprehensive review aims to explore the studies, published since its inception (2010s) to the present, on bioabsorbable composite materials based on PLA and PCL polymeric matrix reinforced with Mg, which is also bioabsorbable and has recognized osteoinductive capacity. The research collected in the literature reveals studies based on different manufacturing and dispersion processes of the reinforcement as well as the physicochemical analysis and corresponding biological evaluation to know the osteoinductive capacity of the proposed PLA/Mg and PCL/Mg composites. In short, this review shows the potential of these composite materials and serves as a guide for those interested in bioabsorbable materials applied in bone tissue engineering.

Cell response and bone ingrowth to 3D printed Ti6Al4V scaffolds with Mg-incorporating sol-gel Ta2O5 coating

In recent years, additive manufacturing techniques have been used to fabricate 3D titanium (Ti)-based scaffolds for production of desirable complex shapes. However, insufficient osteointegration of porous Ti-based scaffolds can elicit long-term complications (e.g., aseptic loosening) and need further revision surgery. In this study, a magnesium (Mg)-incorporating tantalum (Ta) coating was deposited on a 3D Ti6Al4V scaffold using a sol-gel method for enhancing its osteogenic properties. To evaluate the biofunction of this surface, bone mesenchymal stem cells and rabbit femoral condyle were used to assess the cell response and bone ingrowth, respectively. Ta2O5 coatings and Mg-incorporating Ta2O5 coatings were both homogeneously deposited on porous scaffolds. In vitro studies revealed that both coatings exhibit enhanced cell proliferation, ALP activity, osteogenic gene expression and mineralization compared with the uncoated Ti6Al4V scaffold. Especially for Mg-incorporating Ta2O5 coatings, great improvements were observed. In vivo studies, including radiographic examination, fluorochrome labeling and histological evaluation also followed similar trends. Also, bone ingrowth to scaffolds with Mg-incorporating Ta2O5 coatings exhibited the most significant increase compared with uncoated and Ta2O5 coated scaffolds. All the above results indicate that Mg-doped Ta2O5 coatings are an effective tool for facilitating osteointegration of conventional porous Ti6Al4V scaffolds.

Microarray illustrates enhanced mechanistic action towards osteogenesis for magnesium aluminate spinel ceramic-based polyphasic composite scaffold with mesenchymal stem cells and bone morphogenetic protein 2

Spinel (magnesium aluminate MgAl2 O4 ) ceramic-based polyphasic composite scaffold has been recently reported for craniofacial bone tissue engineering. Improving the osteogenic effects of such composite scaffolds with bone morphogenetic proteins (BMP2) is an intensely researched area. This study investigated the gene interactions of this scaffold with BMP2 and mesenchymal stem cells (MSCs). Human bone marrow MSCs were cultured in 3 groups: Group 1-Control (BMSCs), Group 2-BMSC with BMP2, and Group 3-BMSC with scaffold and BMP2. After RNA isolation, gene expression analysis was done by microarray. Differentially expressed genes (DEGs) (-1.0 > fold changes>1 and p value <.05) were studied for their function and gene ontologies using Database for Annotation, Visualization and Integrated Discovery (DAVID). They were further studied by protein-protein interaction network analysis using STRING and MCODE Cytoscape plugin database. Group 3 showed up regulation of 3222 genes against 2158 of Group 2. Group 3 had five annotation clusters with enrichment scores from 2.08 to 3.93. Group 2 had only one cluster. Group 3 showed activation of all major osteogenic pathways: TGF, BMP2, WNT, SMAD, and Notch gene signaling with effects of calcium and magnesium released from the scaffold. Downstream effect of all these caused significant activation of RUNX2, the key transcriptional regulator of osteogenesis in Group 3. STRING and MCODE Cytoscape plugin demonstrated the interactions. The enhanced MSC differentiation for osteogenesis with the addition of BMP2 to the polyphasic composite scaffold proposed promising clinical applications for bone tissue engineering.

Silica Replicas Derived from Mammalian Cells as an Innovative Approach to Physically Direct Cell Lineage Decisions of Mesenchymal Stem Cells

By means of a "live-cell" template strategy, silica replicas displaying the same morphology and topography of the mammalian cells used as templates are fabricated. The replicas are used as substrates to direct the differentiation of mesenchymal stem cells (MSCs) to predefined cell lineages. Upregulation of specific genes shows how the silica replica-based substrates have the ability to induce the molecular characteristics of the mature cell types from which they have been derived from. Thus, MSCs cultured in the presence of silica replicas of human osteoblasts (HObs) differentiate into HObs-like cells, as shown by the upregulation of specific osteogenic genes. Likewise, when MSCs are incubated with silica replicas derived from human chondrocytes, an enhanced expression of chondrogenic markers is observed. Importantly, the effects of the silica replicas are cell type-specific since the incubation of MSCs with HObs silica replicas does not result in upregulation of chondrogenic markers and vice versa. What is more, for both cases, the differentiation rate is enhanced when the silica replicas are used in combination with growth factors, suggesting a potential synergistic effect. These results demonstrate the potential of this innovative method as an efficient and cheap approach with the potential to eliminate, or at least reduce, the use of biochemically soluble compounds in stem cells research.

Surface modification of titanium implants with Mg-containing coatings to promote osseointegration

Titanium (Ti) and Ti alloys are commonly used in dental implants, which have good biocompatibility, mechanical strength, processability, and corrosion resistance. However, the surface inertia of Ti implants leads to delayed integration of Ti and new bone, as well as problems such as aseptic loosening and inadequate osseointegration. Magnesium (Mg) ions can promote bone regeneration, and many studies have used Mg-containing materials to modify the Ti implant surface. This systematic review summarizes the methods, effects, and clinical applications of surface modification of Ti implants with Mg-containing coatings. Database collection was completed on Janury 1, 2023, and a total of 29 relevant studies were ultimately included. Mg can be compounded with different materials and coated to the surface of Ti implants using different methods. In vitro and in vivo experiments have shown that Mg-containing coatings promote cell adhesion and osteogenic differentiation. On the one hand, the surface roughness of implants increases with the addition of Mg-containing coatings, which is thought to have an impact on the osseointegration of the implant. On the other hand, Mg ions promote cell attachment through binding interactions between the integrin family and FAK-related signaling pathways. And Mg ions could induce osseointegration by activating PI3K, Notch, ERK/c-Fos, BMP-4-related signaling pathways and TRPM7 protein channels. Overall, Mg-based coatings show great potential for the surface modification of Ti implants to promote osseointegration. STATEMENT OF SIGNIFICANCE: The inertia surface of titanium (Ti) implants leads to delayed osseointegration. Magnesium (Mg) ions, known for promoting bone regeneration, have been extensively studied to modify the surface of Ti implants. However, no consensus has been reached on the appropriate processing methods, surface roughness and effective concentration of Mg-containing coatings for osseointegration. This systematic review focus on the surface modification of Ti implants with Mg-containing compounds, highlighting the effects of Mg-containing coatings on the surface properties of Ti implants and its associated mechanisms. Besides, we also provide an outlook on future directions to promote the clinical application of Mg-modified implants.

The Role of Trace Elements and Minerals in Osteoporosis: A Review of Epidemiological and Laboratory Findings

The objective of the present study was to review recent epidemiological and clinical data on the association between selected minerals and trace elements and osteoporosis, as well as to discuss the molecular mechanisms underlying these associations. We have performed a search in the PubMed-Medline and Google Scholar databases using the MeSH terms "osteoporosis", "osteogenesis", "osteoblast", "osteoclast", and "osteocyte" in association with the names of particular trace elements and minerals through 21 March 2023. The data demonstrate that physiological and nutritional levels of trace elements and minerals promote osteogenic differentiation through the up-regulation of BMP-2 and Wnt/β-catenin signaling, as well as other pathways. miRNA and epigenetic effects were also involved in the regulation of the osteogenic effects of trace minerals. The antiresorptive effect of trace elements and minerals was associated with the inhibition of osteoclastogenesis. At the same time, the effect of trace elements and minerals on bone health appeared to be dose-dependent with low doses promoting an osteogenic effect, whereas high doses exerted opposite effects which promoted bone resorption and impaired bone formation. Concomitant with the results of the laboratory studies, several clinical trials and epidemiological studies demonstrated that supplementation with Zn, Mg, F, and Sr may improve bone quality, thus inducing antiosteoporotic effects.

Brushite-coated Mg-Nd-Zn-Zr alloy promotes the osteogenesis of vertebral laminae through IGF2/PI3K/AKT signaling pathway

Biodegradable magnesium (Mg) alloys have been extensively investigated in orthopedic implants due to their suitable mechanical strength and high biocompatibility. However, no studies have reported whether Mg alloys can be used to repair lamina defects, and the biological mechanisms regulating osteogenesis are not fully understood. The present study developed a lamina reconstruction device using our patented biodegradable Mg-Nd-Zn-Zr alloy (JDBM), and brushite (CaHPO₄·2H₂O, Dicalcium phosphate dihydrate, DCPD) coating was developed on the implant. Through in vitro and in vivo experiments, we evaluated the degradation behavior and biocompatibility of DCPD-JDBM. In addition, we explored the potential molecular mechanisms by which it regulates osteogenesis. In vitro, ion release and cytotoxicity tests revealed that DCPD-JDBM had better corrosion resistance and biocompatibility. We found that DCPD-JDBM extracts could promote MC3T3-E1 osteogenic differentiation via the IGF2/PI3K/AKT pathway. The lamina reconstruction device was implanted on a rat lumbar lamina defect model. Radiographic and histological analysis showed that DCPD-JDBM accelerated the repair of rat lamina defects and exhibited lower degradation rate compared to uncoated JDBM. Immunohistochemical and qRT-PCR results showed that DCPD-JDBM promoted osteogenesis in rat laminae via IGF2/PI3K/AKT pathway. This study shows that DCPD-JDBM is a promising biodegradable Mg-based material with great potential for clinical applications.

Magnesium Ions Promote In Vitro Rat Bone Marrow Stromal Cell Angiogenesis Through Notch Signaling

Bone defects are often caused by trauma or surgery and can lead to delayed healing or even bone nonunion, thereby resulting in impaired function of the damaged site. Magnesium ions and related metallic materials play a crucial role in repairing bone defects, but the mechanism remains unclear. In this study, we induced the angiogenic differentiation of bone marrow stromal cells (BMSCs) with different concentrations of magnesium ions. The mechanism was investigated using γ-secretase inhibitor (DAPT) at different time points (7 and 14 days). Angiogenesis, differentiation, migration, and chemotaxis were detected using the tube formation assay, wound-healing assay, and Transwell assay. Besides, we analyzed mRNA expression and the angiogenesis-related protein levels of genes by RT-qPCR and western blot. We discovered that compared with other concentrations, the 5 mM magnesium ion concentration was more conducive to forming tubes. Additionally, hypoxia-inducible factor 1 alpha (Hif-1α) and endothelial nitric oxide (eNOS) expression both increased (p < 0.05). After 7 and 14 days of induction, 5 mM magnesium ion group tube formation, migration, and chemotaxis were enhanced, and the expression of Notch pathway genes increased. Moreover, expression of the Notch target genes hairy and enhancer of split 1 (Hes1) and Hes5 (hairy and enhancer of split 5), as well as the angiogenesis-related genes Hif-1α and eNOS, were enhanced (p < 0.05). However, these trends did not occur when DAPT was applied. This indicates that 5 mM magnesium ion is the optimal concentration for promoting the angiogenesis and differentiation of BMSCs in vitro. By activating the Notch signaling pathway, magnesium ions up-regulate the downstream genes Hes1 and Hes5 and the angiogenesis-related genes Hif-1α and eNOS, thereby promoting the angiogenesis differentiation of BMSCs. Additionally, magnesium ion-induced differentiation enhances the migration and chemotaxis of BMSCs. Thus, we can conclude that magnesium ions and related metallic materials promote angiogenesis to repair bone defects. This provides the rationale for developing artificial magnesium-containing bone materials through tissue engineering.

Notch-RBPJ Pathway for the Differentiation of Bone Marrow Mesenchymal Stem Cells in Femoral Head Necrosis

Femoral head necrosis (FHN) is a common leg disease in broilers, resulting in economic losses in the poultry industry. The occurrence of FHN is closely related to the decrease in the number of bone marrow mesenchymal stem cells (BMSCs) and the change in differentiation direction. This study aimed to investigate the function of differentiation of BMSCs in the development of FHN. We isolated and cultured BMSCs from spontaneous FHN-affected broilers and normal broilers, assessed the ability of BMSCs into three lineages by multiple staining methods, and found that BMSCs isolated from FHN-affected broilers demonstrated enhanced lipogenic differentiation, activated Notch-RBPJ signaling pathway, and diminished osteogenic and chondrogenic differentiation. The treatment of BMSCs with methylprednisolone (MP) revealed a significant decrease in the expressions of Runx2, BMP2, Col2a1 and Aggrecan, while the expressions of p-Notch1/Notch1, Notch2 and RBPJ were increased significantly. Jagged-1 (JAG-1, Notch activator)/DAPT (γ-secretase inhibitor) could promote/inhibit the osteogenic or chondrogenic ability of MP-treated BMSCs, respectively, whereas the differentiation ability of BMSCs was restored after transfection with si-RBPJ. The above results suggest that the Notch-RBPJ pathway plays important role in FHN progression by modulating the osteogenic and chondrogenic differentiation of BMSCs.

MicroRNAs-mediated regulation pathways in rheumatic diseases

Rheumatoid arthritis (RA) and ankylosing spondylitis (AS) are two common rheumatic disorders marked by persistent inflammatory joint disease. Patients with RA have osteodestructive symptoms, but those with AS have osteoproliferative manifestations. Ligaments, joints, tendons, bones, and muscles are all affected by rheumatic disorders. In recent years, many epigenetic factors contributing to the pathogenesis of rheumatoid disorders have been studied. MicroRNAs (miRNAs) are small, non-coding RNA molecules implicated as potential therapeutic targets or biomarkers in rheumatic diseases. MiRNAs play a critical role in the modulation of bone homeostasis and joint remodeling by controlling fibroblast-like synoviocytes (FLSs), chondrocytes, and osteocytes. Several miRNAs have been shown to be dysregulated in rheumatic diseases, including miR-10a, 16, 17, 18a, 19, 20a, 21, 27a, 29a, 34a, 103a, 125b, 132, 137, 143, 145, 146a, 155, 192, 203, 221, 222, 301a, 346, and 548a.The major molecular pathways governed by miRNAs in these cells are Wnt, bone-morphogenic protein (BMP), nuclear factor (NF)-κB, receptor activator of NF-κB (RANK)-RANK ligand (RANKL), and macrophage colony-stimulating factor (M-CSF) receptor pathway. This review aimed to provide an overview of the most important signaling pathways controlled by miRNAs in rheumatic diseases.

Mesenchymal cell TRPM7 expression is required for bone formation via the regulation of chondrogenesis

Transient receptor potential melastatin-subfamily member 7 (TRPM7) is a bifunctional protein containing a kinase fused to an ion channel permeated with cations, including Ca²⁺ and Mg²⁺. Trpm7-null mice show embryonic lethality. Paired related homeobox 1 (Prx1) is expressed in undifferentiated mesenchymal cells such as the progenitor cells of both chondrocytes and osteoblasts involved in limb skeleton formation. Prx1-Cre-dependent Trpm7 mesenchymal-deleted mice were generated to examine the role of TRPM7 in bone development. We found that Prx1-Cre;Trpm7^fl/fl mice had shortened bones and impaired trabecular bone formation. Trabecular bone parameters, such as the bone volume (BV/TV), and trabecular number (Tb.N), were decreased in Prx1-Cre;Trpm7^fl/fl mice. The cortical bone parameters of cortical bone area (Ct.Ar) and cortical bone thickness (Ct.Th) were also down-regulated in these mice. The bone formation rate in Prx1-Cre;Trpm7^fl/fl mice was unchanged, but the hypertrophic area and cell size of the zone were smaller, and the expression of Col2a1, Col10a1 and Mmp13 was downregulated compared with control mice. These findings suggest impaired chondrogenesis in Prx1-Cre;Trpm7^fl/fl mice compared to control mice. The receptor activator of nuclear factor-kappa B ligand (RANKL) expression was increased, and RANKL-positive cells and osteoclasts were markedly accumulated in the boundary region between the growth plate and trabecular bone. In contrast, TRPM7 KR mice, which are kinase-dead mutants in which the TRPM7 ion channel function has not been altered, showed no marked differences in trabecular or cortical bone parameters compared to wild-type mice. These findings suggest that TRPM7 is critical as a cation channel rather than as a kinase in bone development via the regulation of chondrogenesis.

Epigenetics: Novel crucial approach for osteogenesis of mesenchymal stem cells

Bone has a robust regenerative potential, but its capacity to repair critical-sized bone defects is limited. In recent years, stem cells have attracted significant interest for their potential in tissue engineering. Applying mesenchymal stem cells (MSCs) for enhancing bone regeneration is a promising therapeutic strategy. However, maintaining optimal cell efficacy or viability of MSCs is limited by several factors. Epigenetic modification can cause changes in gene expression levels without changing its sequence, mainly including nucleic acids methylation, histone modification, and non-coding RNAs. This modification is believed to be one of the determinants of MSCs fate and differentiation. Understanding the epigenetic modification of MSCs can improve the activity and function of stem cells. This review summarizes recent advances in the epigenetic mechanisms of MSCs differentiation into osteoblast lineages. We expound that epigenetic modification of MSCs can be harnessed to treat bone defects and promote bone regeneration, providing potential therapeutic targets for bone-related diseases.

circSKIL promotes osteoblastic differentiation of periodontal ligament cells by sponging miR-532-5p to activate Notch signaling

BACKGROUND AND OBJECTIVE

Periodontal ligament cells (PDLCs) possess the capacity to differentiate into a variety of cell types to benefit periodontal regeneration. In this study, we examined the circSKIL/miR-532-5p/Notch1 axis in controlling the osteoblastic differentiation of PDLCs.

METHODS

Primary human PDLCs (hPDLCs) were isolated and induced to differentiate into osteoblasts. Osteogenic responses were assessed for the expressions of osteoblast-related marker proteins (including alkaline phosphatase (ALP), osteocalcin (OCN), bone morphogenetic protein-2 (BMP2), and runt-related transcription factor 2 (RUNX2) by RT-PCR. The formation of mineralized nodules was examined by Alizarin Red S (ARS) staining and ALP activity. Expressions of circSKIL, miR-532-5p, and Notch1 were measured by RT-PCR and western blotting, and their regulations by combining bioinformatic analysis and luciferase reporter assay. Notch signaling was assessed for the expressions of hairy and enhancer of split-1 (HES1) and Notch intracellular domain (NICD).

RESULTS

During osteoblastic differentiation of hPDLCs, circSKIL, and Notch1 were up-regulated, while miR-532-5p down-regulated. By sponging miR-532-5p, circSKIL activated Notch signaling, increasing levels of Notch1, HES1, and NICD. Functionally, knocking down circSKIL or overexpressing miR-532-5p inhibited osteoblastic differentiation of PDLCs, down-regulating ALP, OCN, BMP2, and RUNX2, and reducing ARS staining or ALP activity. The impacts of circSKIL knockdown were rescued by miR-532-5p inhibitor or overexpressing Notch1, while those caused by up-regulating miR-532-5p were reversed by overexpressing Notch1.

CONCLUSION

By targeting miR-532-5p and up-regulating Notch1, circSKIL critically controls osteoblastic differentiation of hPDLCs. Therefore, modulating this axis may maximize the differentiation of PDLCs into osteoblasts and benefit periodontal regeneration.

Solid‐state NMR ( SSNMR ) Characterization of Osteoblast from Mesenchymal Stromal Cell Differentiation to Osteoblast Mineralization

Solid‐state nuclear magnetic resonance (SSNMR), a technique capable of studying solid or semisolid biological samples, was first applied to study the cell differentiation and mineralization using the whole‐cell sample. Mesenchymal stromal cells (MSCs) with multipotent differentiation capacity were induced to differentiate into osteoblasts. The whole differentiation process, osteoblast mineralization and the mineral maturation, was investigated using SSNMR, providing intact, atomic level information on the cellular mineral structural transformation. Our research indicated the extent of osteoblast mineralization could vary significantly for different cell populations whereas the difference was not easily shown by other means of characterization. The SSNMR spectra revealed hydroxylapatite (or hydroxyapatite [HAP]) formation around 2 to 4 weeks after osteogenic induction for MSCs with a high differentiation potency. The early mineral phase deposit before HAP formation contained a high amount of HPO₄²⁻. The structures of minerals in the extracellular matrix (ECM) of osteoblasts could evolve for a period of time, even after the incubation of cells has been stopped. This observation was only possible by studying the sample in an intact state, where ECM was not disturbed. These findings improved our understanding of MSCs, which had wide applications in bone regeneration and tissue engineering. Meanwhile, this work demonstrated the advantage of studying these cellular systems as a whole without any mineral extraction, which had been largely overlooked. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

The Effect of Ca2+ and Mg2+ Ions Loaded at Degradable PLA Membranes on the Proliferation and Osteoinduction of MSCs

Biodegradable membranes, including Polylactic acid (PLA)-based membranes, are commonly used in bone-tissue-related clinical procedures as biointerface to promote bone tissue regeneration. Calcium (Ca²⁺) and Magnesium (Mg²⁺) ions have been related to the promotion of osteogenesis, where the PLA membranes could be used as carrier and delivery substrate for them to provide osteogenic properties to this material. For this aim, a new ion delivery system based on biodegradable PLA membranes loaded with Mg and hydroxyapatite (HA) particles has been processed by the combination of tape casting and colloidal route. Materials characterization shows that the incorporation of Mg and HA particles changes the surface and hydrophobicity of the PLA membrane, and the in vitro degradation test shows Mg²⁺ and Ca²⁺ ion release and occasionally the precipitation of different ion species onto the membrane surface. Mouse and human Mesenchymal Stem Cells (MSC) were used to define the biocompatibility and bioactivity of these PLA membrane composites, and data indicated Mg²⁺ promotes cell proliferation and potentiates osteoinductive signals, while Ca²⁺ induces the expression of ALP osteogenic marker in human MSCs. Biodegradable PLA membranes loaded with Mg and HA particles is a promising new ion delivery system of Mg²⁺ and Ca²⁺ ions that provides osteogenic signals and works as functional biointerface interfaces with bone tissues.

Regulation of Magnesium Matrix Composites Materials on Bone Immune Microenvironment and Osteogenic Mechanism

Despite magnesium based metal materials are widely used in bone defect repair, there are still various deficiencies, and their properties need to be optimized. Composites synthesized with magnesium based metal as matrix are the research hotspot, and the host immune response after biomaterial implantation is very important for bone binding. By studying the immunoregulation of bone biomaterials, it can regulate the immune response in the process of osteogenesis and create a good local immune microenvironment, which is conducive to biomaterials to reduce inflammatory response and promote good bone binding. This article introduces the osteogenic mechanism of magnesium based metal materials and its regulation on bone immune microenvironment in detail.

Characteristics and regulation of mesenchymal stem cell plasticity by the microenvironment — specific factors involved in the regulation of MSC plasticity

Mesenchymal stem cells (MSCs), multipotent stromal cells, have attracted extensive attention in the field of regenerative medicine and cell therapy due to the capacity of self-renewal, multilineage differentiation, and immune regulation. MSCs have different cellular effects in different diseases, and even have markedly different curative effects with different tissue sources, indicating the plasticity of MSCs. The phenotypes, secreted factors, and proliferative, migratory, differentiating, and immunomodulatory effects of MSCs depend on certain mediators present in their microenvironment. Understanding microenvironmental factors and their internal mechanisms in MSC responses may help in subsequent prediction and improvement of clinical benefits. This review highlighted the recent advances in MSC plasticity in the physiological and pathological microenvironment and multiple microenvironmental factors regulating MSC plasticity. It also highlighted some progress in the underlying molecular mechanisms of MSC remodeling in the microenvironment. It might provide references for the improvement in vitro culture of MSCs, clinical application, and in vivo induction.

The Impact of Trace Elements on Osteoarthritis

Osteoarthritis (OA) is a progressive degenerative disease characterized by cartilage degradation, synovial inflammation, subchondral sclerosis and osteophyte formation. It has a multifactorial etiology with potential contributions from heredity, endocrine function, abnormal mechanical load and nutrition. Of particular considerations are trace element status. Several trace elements, such as boron and magnesium are essential for normal development of the bone and joint in human. While cadmium correlates with the severity of OA. The present review focuses on the roles of trace elements (boron, cadmium, copper, iron, magnesium, manganese, selenium, zinc) in OA and explores the mechanisms by which they act.

The effects of a 3D-printed magnesium-/strontium-doped calcium silicate scaffold on regulation of bone regeneration via dual-stimulation of the AKT and WNT signaling pathways

Numerous studies have demonstrated that calcium silicate (CS) can be doped with various trace metal elements such as strontium (Sr) or magnesium (Mg). These studies have confirmed that such modifications promote bone regeneration. However, the development and emergence of 3D printing have further made it possible to fabricate bone grafts with precise structural designs using multi-bioceramics so as to better suit specific clinical requirements. We fabricated scaffolds using Mg-doped CS as the outer layer with Sr-doped CS in the center. In addition, PCL was used to improve printability of the scaffolds. This enhanced Mg and Sr architecture prevented premature degradation of the scaffolds during immersion while enabling the release of ions in a sustained manner in order to achieve the desired therapeutic goals. Even the capabilities of stem cells were shown to be enhanced when cultured on these scaffolds. Furthermore, the hybrid scaffolds were found to up-regulate the expression of bone-related proteins such as factors leading to differentiation-inducing pathways, including PI3K/Akt, Wnt, and TRPM7. The in vivo performance of the proposed scaffolds was assessed using micro-CT. The histological results revealed that the hybrid scaffolds were able to further enhance bone regeneration as compared to uni-bioceramics. By combining 3D printing, multi-ceramics, and trace metal elements, a novel hybrid scaffold could be fabricated with ease and specifically suited to future bone tissue engineering applications.

Osteogenic Potential of Magnesium (Mg)-Doped Multicomponent Bioactive Glass: In Vitro and In Vivo Animal Studies

The use of bioactive glasses (BGs) has been quite fruitful in hard tissue engineering due to the capability of these materials to bond to living bone. In this work, a melt-derived magnesium (Mg)-doped BG (composition: 45SiO₂–3P₂O₅–26CaO–15Na₂O–7MgO–4K₂O (mol.%)) was synthesized for being used in bone reconstruction. The prepared BGs were then manufactured as three-dimensional (3D) scaffolds by using the sponge replica approach. The microstructure of the samples was assessed by X-ray diffraction (XRD) and the surface morphology was observed by using scanning electron microscopy (SEM). The in vitro bioactivity and the release of osteo-stimulatory Mg²⁺ ions from the prepared samples were investigated over 7 days of incubation in simulated body fluids (SBF). In vitro cellular analyses revealed the compatibility of the Mg-doped BGs with human osteosarcoma cells (MG-63 cell line). Moreover, the Mg-doped BGs could induce bone nodule formation in vitro and improve the migratory ability of human umbilical vein endothelial cells (HUVECs). In vivo osteogenic capacity was further evaluated by implanting the BG-derived scaffolds into surgically-created critical-size bone defects in rats. Histological and immunohistological observations revealed an appropriate bone regeneration in the animals receiving the glass-based scaffolds after 12 weeks of surgery. In conclusion, our study indicates the effectiveness of the Mg-doped BGs in stimulating osteogenesis in both in vitro and in vivo conditions.

Hybrid biofabrication of 3D osteoconductive constructs comprising Mg-based nanocomposites and cell-laden bioinks for bone repair

Tissue engineering approaches for bone repair have rapidly evolved due to the development of novel biofabrication technologies, providing an opportunity to fabricate anatomically-accurate living implants with precise placement of specific cell types. However, limited availability of biomaterial inks, that can be 3D-printed with high resolution, while providing high structural support and the potential to direct cell differentiation and maturation towards the osteogenic phenotype, remains an ongoing challenge. Aiming towards a multifunctional biomaterial ink with high physical stability and biological functionality, this work describes the development of a nanocomposite biomaterial ink (Mg-PCL) comprising of magnesium hydroxide nanoparticles (Mg) and polycaprolactone (PCL) thermoplastic for 3D printing of strong and bioactive bone regenerative scaffolds. We characterised the Mg nanoparticle system and systematically investigated the cytotoxic and osteogenic effects of Mg supplementation to human mesenchymal stromal cells (hMSCs) 2D-cultures. Next, we prepared Mg-PCL biomaterial ink using a solvent casting method, and studied the effect of Mg over mechanical properties, printability and scaffold degradation. Furthermore, we delivered MSCs within Mg-PCL scaffolds using a gelatin-methacryloyl (GelMA) matrix, and evaluated the effect of Mg over cell viability and osteogenic differentiation. Nanocomposite Mg-PCL could be printed with high fidelity at 20 wt% of Mg content, and generated a mechanical reinforcement between 30%-400% depending on the construct internal geometry. We show that Mg-PCL degrades faster than standard PCL in an accelerated-degradation assay, which has positive implications towards in vivo implant degradation and bone regeneration. Mg-PCL did not affect MSCs viability, but enhanced osteogenic differentiation and bone-specific matrix deposition, as demonstrated by higher ALP/DNA levels and Alizarin Red calcium staining. Finally, we present proof of concept of Mg-PCL being utilised in combination with a bone-specific bioink (Sr-GelMA) in a coordinated-extrusion bioprinting strategy for fabrication of hybrid constructs with high stability and synergistic biological functionality. Mg-PCL further enhanced the osteogenic differentiation of encapsulated MSCs and supported bone ECM deposition within the bioink component of the hybrid construct, evidenced by mineralised nodule formation, osteocalcin (OCN) and collagen type-I (Col I) expression within the bioink filaments. This study demonstrated that magnesium-based nanocomposite bioink material optimised for extrusion-based 3D printing of bone regenerative scaffolds provide enhanced mechanical stability and bone-related bioactivity with promising potential for skeletal tissue regeneration.

Microfibrillar-associated protein 5 regulates osteogenic differentiation by modulating the Wnt/β-catenin and AMPK signaling pathways

Background

Dysfunctional osteogenesis of bone marrow mesenchymal stem cells (BMSCs) plays an important role in osteoporosis occurrence and development. However, the molecular mechanisms of osteogenic differentiation remain unclear. This study explored whether microfibrillar-associated protein 5 (MFAP5) regulated BMSCs osteogenic differentiation.

Methods

We used shRNA or cDNA to knock down or overexpress MFAP5 in C3H10 and MC3T3-E1 cells. AR-S- and ALP-staining were performed to quantify cellular osteogenic differentiation. The mRNA levels of the classical osteogenic differentiation biomarkers Runx2, Col1α1, and OCN were quantified by qRT-PCR. Finally, we employed Western blotting to measure the levels of Wnt/β-catenin and AMPK signaling proteins.

Results

At days 0, 3, 7, and 14 after osteogenic induction, AR-S- and ALP-staining was lighter in MFAP5 knockdown compared to control cells, as were the levels of Runx2, Col1α1 and OCN. During osteogenesis, the levels of β-catenin, p-GSK-3β, AMPK, and p-AMPK were upregulated, while that of GSK-3β was downregulated, indicating that Wnt/β-catenin and AMPK signaling were activated. The relevant molecules were expressed at lower levels in the knockdown than control group; the opposite was seen for overexpressing cell lines.

Conclusions

MFAP5 regulates osteogenesis via Wnt/β‑catenin- and AMPK-signaling; MFAP5 may serve as a therapeutic target in patients with osteoporosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00413-0.

Characterization and in vitro assessment of three-dimensional extrusion Mg-Sr codoped SiO2-complexed porous microhydroxyapatite whisker scaffolds for biomedical engineering

BACKGROUND

Large bone defects have always been a great challenge for orthopedic surgeons. The use of a good bone substitute obtained by bone tissue engineering (BTE) may be an effective treatment method. Artificial hydroxyapatite, a commonly used bone defect filler, is the main inorganic component of bones. Because of its high brittleness, fragility, and lack of osteogenic active elements, its application is limited. Therefore, its fragility should be reduced, its osteogenic activity should be improved, and a more suitable scaffold should be constructed.

METHODS

In this study, a microhydroxyapatite whisker (mHAw) was developed, which was doped with the essential trace active elements Mg2+ and Sr2+ through a low-temperature sintering technique. After being formulated into a slurry, a bionic porous scaffold was manufactured by extrusion molding and freeze drying, and then SiO2 was used to improve the mechanical properties of the scaffold. The hydrophilicity, pore size, surface morphology, surface roughness, mechanical properties, and release rate of the osteogenic elements of the prepared scaffold were detected and analyzed. In in vitro experiments, Sprague-Dawley (SD) rat bone marrow mesenchymal stem cells (rBMSCs) were cultured on the scaffold to evaluate cytotoxicity, cell proliferation, spreading, and osteogenic differentiation.

RESULTS

Four types of scaffolds were obtained: mHAw-SiO2 (SHA), Mg-doped mHAw-SiO2 (SMHA), Sr-doped mHAw-SiO2 (SSHA), and Mg-Sr codoped mHAw-SiO2 (SMSHA). SHA was the most hydrophilic (WCA 5°), while SMHA was the least (WCA 8°); SMHA had the smallest pore size (247.40 ± 23.66 μm), while SSHA had the largest (286.20 ± 19.04 μm); SHA had the smallest Young's modulus (122.43 ± 28.79 MPa), while SSHA had the largest (188.44 ± 47.89 MPa); and SHA had the smallest compressive strength (1.72 ± 0.29 MPa), while SMHA had the largest (2.47 ± 0.25 MPa). The osteogenic active elements Si, Mg, and Sr were evenly distributed and could be sustainably released from the scaffolds. None of the scaffolds had cytotoxicity. SMSHA had the highest supporting cell proliferation and spreading rate, and its ability to promote osteogenic differentiation of rBMSCs was also the strongest.

CONCLUSIONS

These composite porous scaffolds not only have acceptable physical and chemical properties suitable for BTE but also have higher osteogenic bioactivity and can possibly serve as potential bone repair materials.

LncRNA expression profile analysis of Mg2+-induced osteogenesis by RNA-seq and bioinformatics

BACKGROUND

In recent years, magnesium (Mg) has been extensively studied for manufacturing biodegradable orthopedic devices. Besides other advantages, researches have shown that magnesium-based implants can stimulate osteogenesis thus accelerating orthopedic trauma recovery, but its molecular mechanism is not fully understood. Meanwhile, long non-coding RNA (lncRNA) has been found to play vital role in regulating osteogenic differentiation.

OBJECTIVE

To explore the role of lncRNA in Mg2+ (magnesium ions)-induced osteogenesis.

METHODS

The effect of Mg2+ on mBMSCs proliferation was detected by the CCK-8 assay. The optimum concentration of Mg2+ (7.5 mM) in promoting mBMSCs osteogenesis was determined by ALP staining and Alizarin red staining, western blot and RT-qPCR were performed to detect osteogenic markers expressions. The lncRNAs and mRNAs expression profiles of mBMSCs were assessed by RNA-Seq and processed by bioinformatics analysis. The selected lncRNAs expression level was validated by RT-qPCR.

RESULTS

The effect of Mg2+ in promoting osteogenesis was confirmed and the optimum concentration was determined as 7.5 mM. The lncRNAs and mRNAs differentially expressed between 7.5 mM Mg2+-treated group and control group was detected and functional analysis revealed that their function were associated with osteogenesis. The ceRNA networks were constructed for H19 and Dubr that aberrantly expressed in two groups. The ceRNA networks of selected lncRNAs (H19 and Dubr) were constructed.

CONCLUSIONS

This study identified H19 and Dubr as osteogenic associated lncRNAs involved in Mg2+-induced osteogenesis, and they might play their roles through lncRNA-miRNA-mRNA axis.

Vitamin D3/vitamin K2/magnesium-loaded polylactic acid/tricalcium phosphate/polycaprolactone composite nanofibers demonstrated osteoinductive effect by increasing Runx2 via Wnt/β-catenin pathway

Vitamin D₃, vitamin K₂, and Mg (10%, 1.25%, and 5%, w/w, respectively)-loaded PLA (12%, w/v) (TCP (5%, w/v))/PCL (12%, w/v) 1:1 (v/v) composite nanofibers (DKMF) were produced by electrospinning method (ES) and their osteoinductive effects were investigated in cell culture test. Neither pure nanofibers nor DKMF caused a significant cytotoxic effect in fibroblasts. The induction of the stem cell differentiation into osteogenic cells was observed in the cell culture with both DKMF and pure nanofibers, separately. Vitamin D_3, vitamin K₂, and magnesium demonstrated to support the osteogenic differentiation of mesenchymal stem cells by expressing Runx2, BMP2, and osteopontin and suppressing PPAR-γ and Sox9. Therefore, the Wnt/β-catenin signaling pathway was activated by DKMF. DKMF promoted large axonal sprouting and needle-like elongation of osteoblast cells and enhanced cellular functions such as migration, infiltration, proliferation, and differentiation after seven days of incubation using confocal laser scanning microscopy. The results showed that DKMF demonstrated sustained drug release for 144 h, tougher and stronger structure, higher tensile strength, increased water up-take capacity, decreased degradation ratio, and slightly lower Tm and Tg values compared to pure nanofibers. Consequently, DKMF is a promising treatment approach in bone tissue engineering due to its osteoinductive effects.

Proton pump inhibitors and osteoporosis risk: exploring the role of TRPM7 channel

BACKGROUND

Long-term use of proton pump inhibitors (PPIs) has been linked to an increased risk of osteoporosis, with various indirect mechanisms so far identified. Although no direct underlying mechanism for effect on bone cells have been investigated with the use of PPIs. Melastatin-like transient receptor potential 7 (TRPM7)channel has been engaged in the proliferation of bone cells. TRPM7 channel is regulated by extracellular Mg²⁺ and Ca²⁺ level, that further encourages to analyse if any imbalance with pantoprazole usage could alter bone remodelling process mediated by TRPM7.

OBJECTIVES

The present study was conducted to investigate the effect of pantoprazole on the calcium and magnesium level, the cations involved in the bone remodelling process, as well as role of the TRPM7 channel in the proliferation of bone cells.

METHODS

A cytotoxicity study was carried out to study the effect of pantoprazole on the bone cell using MC3T3-E1 cell line, together with the expression of TRPM7 was determined post-pantoprazole treatment. An in vivo study in rats was carried out for estimation of Ca²⁺, Mg²⁺ and Ca²⁺/Mg²⁺ ratio as well as bone strength was measured over a duration of 4 weeks and 8 weeks with the treatment of pantoprazole. A pilot-scale clinical study was carried out in patients with a fracture to support the evidence of preliminary findings from in-vitro and in vivo studies.

RESULTS

MC3T3-E1 cell line treated with pantoprazole showed decreased cell viability in a dose-dependent manner and reduced expression of TRPM7 channel, evidencing interaction of TRPM7 and pantoprazole in the bone remodelling process. A pilot study conducted on 12 patients having major fractures showed changes in serum Mg²⁺ and Ca²⁺ levels over a period of 1 month as well as the animal study also showed ionic imbalance over 8-week treatment with pantoprazole. Bone density measured for the patient at the end of the 1-month treatment was found to be in the osteopenic category, together with the animal study which showed a decrease in femur bone strength for the animal treated with pantoprazole over a period of 8 weeks.

CONCLUSION

The study findings proved a negative impact of pantoprazole use on Ca²⁺ and Mg²⁺ levels, which can impact TRPM7-mediated bone remodelling which serves to be a possible mechanism for osteoporosis upon pantoprazole use.

Controlled co-delivery system of magnesium and lanthanum ions for vascularized bone regeneration

For craniofacial bone regeneration, how to promote vascularized bone regeneration is still a significant problem, and the controlled release of trace elements vital to osteogenesis has attracted attention. In this study, an ion co-delivery system was developed to promote angiogenesis and osteogenesis. Magnesium ions (Mg²⁺) and lanthanum ions (La³⁺) were selected as biosignal molecules because Mg²⁺can promote angiogenesis and both of them can enhance bone formation. Microspheres made of poly(lactide-co-glycolide) were applied to load La₂(CO₃)₃, which was embedded into a MgO/MgCO₃-loaded cryogel made of photocrosslinkable gelatin methacryloyl to enable co-delivery of Mg²⁺and La³⁺. Evaluations of angiogenesis and osteogenesis were conducted via bothin vitrocell culture using human bone marrow mesenchymal stromal cells andin vivoimplantation using a rat model with calvarial defect (5 mm in diameter). Compared to systems releasing only Mg²⁺or La³⁺, the combination system demonstrated more significant effects on blood vessels formation, thereby promoting the regeneration of vascularized bone tissue. At 8 weeks post-implantation, the new bone volume/total bone volume ratio reached a value of 40.1 ± 0.9%. In summary, a properly designed scaffold system with the capacity to release ions of different bioactivities in a desired pattern can be a promising strategy to meet vascularized bone regeneration requirements.

Macrophage-derived oncostatin M/bone morphogenetic protein 6 in response to Mg-based materials influences pro-osteogenic activity of human umbilical cord perivascular cells

Macrophages are the central immune cell involved in the foreign body reaction to the implants. Furthermore, the magnesium-based materials could modulate macrophage functions, and subsequently influence bone formation via not clearly understood mechanisms. To analysis the roles of materials (magnesium and its gadolinium-based alloy; Mg and Mg-10Gd) on secretion of macrophages and their effects on pro-osteogenic activity, human mesenchymal stem cells (MSC) and macrophages were cocultured directly on the materials surface. Here, oncostatin M (OSM) - glycoprotein 130 (gp130) signaling complex as well as BMP6/SMAD were found to be involved in the Mg and Mg-10Gd multifactorial modulating osteogenic differentiation. Furthermore, materials upregulated the gene expression of bone morphogenetic protein 6 (BMP6) in macrophages, as well as its protein receptors and mothers against decapentaplegic homolog (SMAD) 1/4/5 in cocultured MSC. Besides, both materials could reduce the secretion of tumour necrosis factor alpha (TNFα) and interleukin 1 beta (IL1β) in macrophages and cocultures. These results collectively imply that Mg and Mg-10Gd could create a beneficial microenvironment for osteogenic differentiation and further support Mg-based biomaterial immunomodulatory properties by modulating the interactions of macrophages and MSC for bone regeneration. STATEMENT OF SIGNIFICANCE: Mg-activated macrophages could regulate the pro-osteogenic activity via OSM/gp130 and Smad-related signalling. The neutralisation assay was utilised to confirm the hypothesis of inductive osteoblastic differentiation of human MSC via OSM/gp130 signalling. Current study are essential to evidence that the coordinated communication between macrophages and MSC (OSM/gp130/BMP6/TNFα/IL1β), which could be utilised for improving magnesium-based bone biomaterials and therapeutic applications.

Update on the research and development of magnesium-based biodegradable implants and their clinical translation in orthopaedics

Biodegradable magnesium (Mg) or its alloys are desirable materials for development into new-generation internal fixation devices or implants with high biocompatibility, adequate mechanical modulus, and osteopromotive properties, which may overcome some of the drawbacks of the existing permanent orthopaedic implants with regard to stress-shielding of bone and beam-hardening effects on radiographic images. This review summarises the current research status of Mg-based orthopaedic implants in animals and clinical trials. First, detailed information of animal studies including bone fracture repair and anterior cruciate ligament reconstruction with the use of Mg-based orthopaedic devices is introduced. Second, the repair mechanisms of the Mg-based orthopaedic implants are also reviewed. Afterwards, reports of recent clinical cases treated using Mg-based implants in orthopaedics are summarised. Finally, the challenges and the strategies of the use of Mg-based orthopaedic implants are discussed. Taken together, the collected efforts in basic research, translational work, and clinical applications of Mg-based orthopaedic implants over the last decades greatly contribute to the development of a new generation of biodegradable metals used for the design of innovative implants for better treatment of orthopaedic conditions in patients with challenging skeletal disorders or injuries.

Magnesium Picolinate Improves Bone Formation by Regulation of RANK/RANKL/OPG and BMP-2/Runx2 Signaling Pathways in High-Fat Fed Rats

Magnesium (Mg) deficiency may affect bone metabolism by increasing osteoclasts, decreasing osteoblasts, promoting inflammation/oxidative stress, and result in subsequent bone loss. The objective of the present study was to identify the molecular mechanism underlying the bone protective effect of different forms of Mg (inorganic magnesium oxide (MgO) versus organic magnesium picolinate (MgPic) compound) in rats fed with a high-fat diet (HFD). Forty-two Wistar albino male rats were divided into six group (n = 7): (i) control, (ii) MgO, (iii) MgPic, (iv) HFD, (v) HFD + MgO, and (vi) HFD + MgPic. Bone mineral density (BMD) increased in the Mg supplemented groups, especially MgPic, as compared with the HFD group (p < 0.001). As compared with the HFD + MgO group, the HFD + MgPic group had higher bone P (p < 0.05) and Mg levels (p < 0.001). In addition, as compared to MgO, MgPic improved bone formation by increasing the levels of osteogenetic proteins (COL1A1 (p < 0.001), BMP2 (p < 0.001), Runx2 (p < 0.001), OPG (p < 0.05), and OCN (p < 0.001), IGF-1 (p < 0.001)), while prevented bone resorption by reducing the levels of RANK and RANKL (p < 0.001). In conclusion, the present data showed that the MgPic could increase osteogenic protein levels in bone more effectively than MgO, prevent bone loss, and contribute to bone formation in HFD rats.

Double-edged effects caused by magnesium ions and alkaline environment regulate bioactivities of magnesium-incorporated silicocarnotite in vitro

Magnesium (Mg) is an important element for its enhanced osteogenic and angiogenic properties in vitro and in vivo, however, the inherent alkalinity is the adverse factor that needs further attention. In order to study the role of alkalinity in regulating osteogenesis and angiogenesis in vitro, magnesium-silicocarnotite [Mg-Ca₅(PO₄)₂SiO₄, Mg-CPS] was designed and fabricated. In this study, Mg-CPS showed better osteogenic and angiogenic properties than CPS within 10 wt.% magnesium oxide (MgO), since the adversity of alkaline condition was covered by the benefits of improved Mg ion concentrations through activating Smad2/3-Runx2 signaling pathway in MC3T3-E1 cells and PI3K-AKT signaling pathway in human umbilical vein endothelial cells in vitro. Besides, provided that MgO was incorporated with 15 wt.% in CPS, the bioactivities had declined due to the environment consisting of higher-concentrated Mg ions, stronger alkalinity and lower Ca/P/Si ions caused. According to the results, it indicated that bioactivities of Mg-CPS in vitro were regulated by the double-edged effects, which were the consequence of Mg ions and alkaline environment combined. Therefore, if MgO is properly incorporated in CPS, the improved bioactivities could cover alkaline adversity, making Mg-CPS bioceramics promising in orthopedic clinical application for its enhancement of osteogenesis and angiogenesis in vitro.

Mg/Cu-doped TiO2 nanotube array: A novel dual-function system with self-antibacterial activity and excellent cell compatibility

Many studies were conducted to change the surface morphology and chemical composition of Ti implants for the improvement of antibacterial ability and osseointegration between medical Ti and surrounding bone tissue. In this study, we successfully prepared a novel dual-function coating on pure Ti surface, i.e. Cu and Mg-co-doped TiO₂ nanotube (TN) coating, by combining anodisation and hydrothermal treatment (HT), which could act as a delivery platform for the sustained release of Cu and Mg ions. Results showed that the amounts of Cu and Mg were about 5.43 wt%-6.55 wt% and 0.69 wt%-0.73 wt%, respectively. In addition, the surface morphology of Cu and Mg-co-doped TN (CuMTN) coatings transformed into nanoneedles after HT for 1 h. Compared with TN, CuMTN had no change in roughness and remarkable improved hydrophilicity. Antibacterial tests revealed that CuMTN had an antibacterial rate of more than 93% against Escherichia coli and Staphylococcus aureus, thereby showing excellent antibacterial properties. In addition, CuMTN could induce the formation of apatite well after being immersed in simulated body fluid, showing good biological activity. Preosteoblasts (MC3T3-E1) cultured on CuMTN-coated Ti demonstrated better proliferation and osteogenic differentiation than pristine and as-anodised specimens. To the best of our best knowledge, this study had successfully attempted to combine anodisation and HT, introduce Cu/Mg elements and functionalise Ti-based implant surfaces with enhanced hydrophilicity, osteogenesis and antimicrobial properties that can meet clinical needs for the first time.

Cross-Talks between the Cardiovascular Disease-Sarcopenia-Osteoporosis Triad and Magnesium in Humans

Magnesium (Mg) is a pivotal and very complex component of healthy aging in the cardiovascular-muscle-bone triad. Low Mg levels and low Mg intake are common in the general aging population and are associated with poorer outcomes than higher levels, including vascular calcification, endothelial dysfunction, osteoporosis, or muscle dysfunction/sarcopenia. While Mg supplementation appears to reverse these processes and benefit the triad, more randomized clinical trials are needed. These will allow improvement of preventive and curative strategies and propose guidelines regarding the pharmaceutical forms and the dosages and durations of treatment in order to optimize and adapt Mg prescription for healthy aging and for older vulnerable persons with comorbidities.

Biodegradable magnesium combined with distraction osteogenesis synergistically stimulates bone tissue regeneration via CGRP-FAK-VEGF signaling axis

Critical size bone defects are frequently caused by accidental trauma, oncologic surgery, and infection. Distraction osteogenesis (DO) is a useful technique to promote the repair of critical size bone defects. However, DO is usually a lengthy treatment, therefore accompanied with increased risks of complications such as infections and delayed union. Here, we demonstrated that magnesium (Mg) nail implantation into the marrow cavity degraded gradually accompanied with about 4-fold increase of new bone formation and over 5-fold of new vessel formation as compared with DO alone group in the 5 mm femoral segmental defect rat model at 2 weeks after distraction. Mg nail upregulated the expression of calcitonin gene-related peptide (CGRP) in the new bone as compared with the DO alone group. We further revealed that blockade of the sensory nerve by overdose capsaicin blunted Mg nail enhanced critical size bone defect repair during the DO process. CGRP concentration-dependently promoted endothelial cell migration and tube formation. Meanwhile, CGRP promoted the phosphorylation of focal adhesion kinase (FAK) at Y397 site and elevated the expression of vascular endothelial growth factor A (VEGFA). Moreover, inhibitor/antagonist of CGRP receptor, FAK, and VEGF receptor blocked the Mg nail stimulated vessel and bone formation. We revealed, for the first time, a CGRP-FAK-VEGF signaling axis linking sensory nerve and endothelial cells, which may be the main mechanism underlying Mg-enhanced critical size bone defect repair when combined with DO, suggesting a great potential of Mg implants in reducing DO treatment time for clinical applications.

Evaluation of the immunomodulatory effects of cobalt, copper and magnesium ions in a pro inflammatory environment

Biomaterials and scaffolds for Tissue Engineering are widely used for an effective healing and regeneration. However, the implantation of these scaffolds causes an innate immune response in which the macrophage polarization from M1 (pro-inflammatory) to M2 (anti-inflammatory) phenotype is crucial to avoid chronic inflammation. Recent studies have showed that the use of bioactive ions such as cobalt (Co²⁺), copper (Cu²⁺) and magnesium (Mg²⁺) could improve tissue regeneration, although there is limited evidence on their effect on the macrophage response. Therefore, we investigated the immunomodulatory potential of Co²⁺, Cu²⁺ and Mg²⁺ in macrophage polarization. Our results indicate that Mg²⁺ and concentrations of Cu²⁺ lower than 10 μM promoted the expression of M2 related genes. However, higher concentrations of Cu²⁺ and Co²⁺ (100 μM) stimulated pro-inflammatory marker expression, indicating a concentration dependent effect of these ions. Furthermore, Mg²⁺ were able to decrease M1 marker expression in presence of a mild pro-inflammatory stimulus, showing that Mg²⁺ can be used to modulate the inflammatory response, even though their application can be limited in a strong pro-inflammatory environment.

Magnesium oxide-incorporated electrospun membranes inhibit bacterial infections and promote the healing process of infected wounds

Bacterial infections cause severe secondary damage to wounds and hinder wound healing processes. We prepared magnesium oxide (MgO) nanoparticle-incorporated nanofibrous membranes by electrospinning and investigated their potential for wound dressing and fighting bacterial infection. MgO-Incorporated membranes possessed good elasticity and flexibility similar to native skin tissue and were hydrophilic, ensuring comfortable contact with wound beds. The cytocompatibility of membranes was dependent on the amounts of incorporated MgO nanoparticles: lower amounts promoted while higher amounts suppressed the proliferation of fibroblasts, endothelial cells, and macrophages. The antibacterial capacity of membranes was proportional to the amounts of incorporated MgO nanoparticles and they inhibited more than 98% E. coli, 90% S. aureus, and 94% S. epidermidis. MgO nanoparticle-incorporated membranes effectively suppressed bacterial infection and significantly promoted the healing processes of infected full-thickness wounds in a rat model. Subcutaneous implantation demonstrated that the incorporation of MgO nanoparticles into electrospun membranes elevated their bioactivity as evidenced by considerable cell infiltration into their dense nanofiber configuration and enhanced the remodeling of implanted membranes. This study highlights the potential of MgO-incorporated electrospun membranes in preventing bacterial infections of wounds.