High extracellular magnesium inhibits mineralized matrix deposition and modulates intracellular calcium signaling in human bone marrow-derived mesenchymal stem cells

Rapamycin increases murine lifespan but does not reduce mineral volume in the Matrix GLA Protein (MGP) knockout mouse model of medial arterial calcification

Peripheral artery disease (PAD) is the narrowing of the arteries that carry blood to the lower extremities. PAD has been traditionally associated with atherosclerosis. However, recent studies have found that medial arterial calcification (MAC) is the primary cause of chronic limb ischemia below the knee. MAC involves calcification of the elastin fibers surrounding smooth muscle cells (SMCs) in arteries. Matrix GLA Protein (MGP) binds circulating calcium and inhibits vascular calcification. Mgp -/- mice develop severe MAC and die within 8 weeks of birth due to aortic rupture or heart failure. We previously discovered a rare genetic disease Arterial Calcification due to Deficiency in CD73 (ACDC) in which patients present with extensive MAC in their lower extremity arteries. Using a patient-specific induced pluripotent stem cell model we found that rapamycin inhibited calcification. Here we investigated whether rapamycin could reduce MAC in vivo using Mgp -/- mice as a model. Mgp +/+ and Mgp -/- mice received 5mg/kg rapamycin or vehicle. Calcification content was assessed via microCT, and vascular morphology and extracellular matrix content assessed histologically. Immunostaining and western blot analysis were used to examine SMC phenotypes and cellular functions. Rapamycin prolonged Mgp -/- mice lifespan, decreased mineral density in the arteries, and increased smooth muscle actin protein levels, however, calcification volume, vessel morphology, SMC proliferation, and autophagy flux were all unchanged. These findings suggest that rapamycin's effects in the Mgp -/- mouse are independent of the vascular phenotype.

Multiscale morphological analysis of bone microarchitecture around Mg-10Gd implants

The utilization of biodegradable magnesium (Mg)-based implants for restoration of bone function following trauma represents a transformative approach in orthopaedic application. One such alloy, magnesium-10 weight percent gadolinium (Mg-10Gd), has been specifically developed to address the rapid degradation of Mg while enhancing its mechanical properties to promote bone healing. Previous studies have demonstrated that Mg-10Gd exhibits favorable osseointegration; however, it exhibits distinct ultrastructural adaptation in comparison to conventional implants like titanium (Ti). A crucial aspect that remains unexplored is the impact of Mg-10Gd degradation on the bone microarchitecture. To address this, we employed hierarchical three-dimensional imaging using synchrotron radiation in conjunction with image-based finite element modelling. By using the methods outlined, the vascular porosity, lacunar porosity and the lacunar-canaliculi network (LCN) morphology of bone around Mg-10Gd in comparison to Ti in a rat model from 4 weeks to 20 weeks post-implantation was investigated. Our investigation revealed that within our observation period, the degradation of Mg-10Gd implants was associated with significantly lower (p < 0.05) lacunar density in the surrounding bone, compared to Ti. Remarkably, the LCN morphology and the fluid flow analysis did not significantly differ for both implant types. In summary, a more pronounced lower lacunae distribution rather than their morphological changes was detected in the surrounding bone upon the degradation of Mg-10Gd implants. This implies potential disparities in bone remodelling rates when compared to Ti implants. Our findings shed light on the intricate relationship between Mg-10Gd degradation and bone microarchitecture, contributing to a deeper understanding of the implications for successful osseointegration.

Low Magnesium Concentration Enforces Bone Calcium Deposition Irrespective of 1,25-Dihydroxyvitamin D3 Concentration

Efficient coordination between Mg²⁺ and vitamin D maintains adequate Ca²⁺ levels during lactation. This study explored the possible interaction between Mg²⁺ (0.3, 0.8, and 3 mM) and 1,25-dihydroxyvitamin D₃ (1,25D; 0.05 and 5 nM) during osteogenesis using bovine mesenchymal stem cells. After 21 days, differentiated osteocytes were subjected to OsteoImage analysis, alkaline phosphatase (ALP) activity measurements, and immunocytochemistry of NT5E, ENG (endoglin), SP7 (osterix), SPP1 (osteopontin), and the BGLAP gene product osteocalcin. The mRNA expression of NT5E, THY1, ENG, SP7, BGLAP, CYP24A1, VDR, SLC41A1, SLC41A2, SLC41A3, TRPM6, TRPM7, and NIPA1 was also assessed. Reducing the Mg²⁺ concentration in the medium increased the accumulation of mineral hydroxyapatite and ALP activity. There was no change in the immunocytochemical localization of stem cell markers. Expression of CYP24A1 was higher in all groups receiving 5 nM 1,25D. There were tendencies for higher mRNA abundance of THY1, BGLAP, and NIPA1 in cells receiving 0.3 mM Mg²⁺ and 5 nM 1,25D. In conclusion, low levels of Mg²⁺ greatly enhanced the deposition of bone hydroxyapatite matrix. The effect of Mg²⁺ was not modulated by 1,25D, although the expression of certain genes (including BGLAP) tended to be increased by the combination of low Mg²⁺ and high 1,25D concentrations.

AMPK/mTOR Pathway Is Involved in Autophagy Induced by Magnesium-Incorporated TiO2 Surface to Promote BMSC Osteogenic Differentiation

Magnesium has been extensively utilized to modify titanium implant surfaces based on its important function in promoting osteogenic differentiation. Autophagy has been proven to play a vital role in bone metabolism. Whether there is an association between autophagy and magnesium in promoting osteogenic differentiation remains unclear. In the present study, we focused on investigating the role of magnesium ions in early osteogenic activity and the underlying mechanism related to autophagy. Different concentrations of magnesium were embedded in micro-structured titanium surface layers using the micro-arc oxidation (MAO) technique. The incorporation of magnesium benefited cell adhesion, spreading, and viability; attenuated intracellular ATP concentrations and p-mTOR levels; and upregulated p-AMPK levels. This indicates the vital role of the ATP-related AMPK/mTOR signaling pathway in the autophagy process associated with osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) induced by magnesium modification on titanium surfaces. The enhanced osteogenic differentiation and improved cellular autophagy activity of BMSCs in their extraction medium further confirmed the function of magnesium ions. The results of the present study advance our understanding of the mechanism by which magnesium regulates BMSC osteogenic differentiation through autophagy regulation. Moreover, endowing implants with the ability to activate autophagy may be a promising strategy for enhancing osseointegration in the translational medicine field in the future.

A Degradable and Osteogenic Mg-Based MAO-MT-PLGA Drug/Ion Delivery System for Treating an Osteoporotic Fracture

Osteoporotic fractures are a very common bone disease that is difficult to completely cure. A large number of people worldwide suffer from pain caused by osteoporotic fractures every year, which can even cause disability and death. The compromised skeletal strength, lower density, trabecular microstructure, and bone-forming ability caused by osteoporotic fractures make them difficult to treat relative to normal fractures. An ideal scheme for osteoporotic fractures is to select internal fixation materials with matched mechanical and biological properties and carry anti-osteoporosis drugs on the plant to achieve bio-fixation and improve the condition of osteoporosis simultaneously. We designed a Mg-based MAO-MT-PLGA drug/ion delivery system (DDS) compatible with bone-like mechanical properties, degradation properties, and drug therapy. In this research, we evaluated the degradation behavior of Mg-based MAO-MT-PLGA DDS using immersion tests and electrochemical tests aided by SEM, EDS, XPS, XRD, and FT-IR. The DDS showed better corrosion resistance over Mg alloy and could release more Mg2+ due to the degradation of PLGA. According to cell viability and cell adhesion, the DDS showed better osteogenic characteristics over control group I (Mg alloy) and control group II (Mg-based MAO alloy), especially in the cells co-cultured with the leaching solution for 72 h, in which the DDS group increased to about 15% cell viability compared with group I (p < 0.05). The mRNA relative expressions, including ALP, collagen I, OCN, OPG, and Runx-2, as well as extracellular matrix calcium deposits of the DDS, are 1.5~2 times over control group I and control group II (p < 0.05), demonstrating a better ability to promote bone formation and inhibit bone resorption. After the DDS was implanted into the castrated rat model for one month, the trabeculae in the treatment group were significantly denser and stronger than those in the control group, with a difference of about 1.5 times in bone volume fraction, bone density, and the number of trabeculae, as well as the magnesium content in the bone tissue (p < 0.05). The above results demonstrated that the Mg-based MAO-MT-PLGA drug/ion delivery system is a potential treatment for osteoporotic fractures.

3D printed magnesium-doped β-TCP gyroid scaffold with osteogenesis, angiogenesis, immunomodulation properties and bone regeneration capability in vivo

Bioceramics have been used in orthopedic surgery for several years. Magnesium (Mg) is an essential element in bone tissue and plays an important role in bone metabolism. Mg-doped bioceramics has attracted the attention of researchers recently. However, the optimal doping amount of Mg in β-TCP and the immunomodulatory property of Mg-doped β-TCP (Mg-TCP) have not been determined yet. In this study, β-TCP scaffolds doped with different contents of magnesium oxide (0 wt%, 1 wt%, 3 wt%, and 5 wt%) with gyroid structure were printed by digital light processing (DLP) method, and the physicochemical and biological functions were then investigated. Mg-doping improved the physicochemical properties of the β-TCP scaffolds. In vitro experiments confirmed that the doping of Mg in β-TCP scaffolds promoted the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and angiogenic differentiation of endothelial progenitor cells (EPCs), where the 5Mg-TCP has the optimal properties when using the "one cell type" method. It was also found that all Mg-TCP facilitated the polarization of RAW264.7 cells to the M2 phenotype, especially the 3Mg-TCP. However, 3Mg-TCP displayed the optimal osteogenic and angiogenic potential when using a "multiple cell type" method, which referred to culturing the BMSCs or EPCs in the macrophage-conditioned medium. Finally, the in vivo experiments were conducted and the results confirmed that the 3Mg-TCP scaffolds possessed the satisfying bone defect repair capability both after 6 and 12 weeks of implantation. This study suggests that 3Mg-TCP scaffolds provide the optimal biological performance and thus have the potential for clinical translation.

Low Mg content on Ti-Nb-Sn alloy when in contact with eBMMSCs promotes improvement of its biological functions

Magnesium is a metal used in the composition of titanium alloys and imparts porosity. Due to its osteoconductive, biocompatible and biodegradable characteristics, its application in the development of biomedical materials has become attractive. This study aimed to evaluate the influence of magnesium present in porous Ti-Nb-Sn alloys, which have a low elastic modulus in adhesive, osteogenic properties and the amount of reactive intracellular oxygen species released in mesenchymal stem cells derived from bone marrow equine bone (eBMMSCs). Mechanical properties of the alloy, such as hardness, compressive strength and elastic modulus, were analyzed, as well as surface morphological characteristics through scanning electron microscopy. The evaluation of magnesium ion release was performed by atomic force spectroscopy. The biological characteristics of the alloy, when in contact with the alloy surface and with the culture medium conditioned with the alloy, were studied by SEM and optical microscopy. Confirmation of osteogenic differentiation by alizarin red and detection of ROS using a Muse® Oxidative Stress Kit based on dihydroetide (DHE). The alloy showed an elastic modulus close to cortical bone values. The hardness was close to commercial Ti grade 2, and the compressive strength was greater than the value of cortical bone. The eBMMSCs adhered to the surface of the alloy during the experimental time. Osteogenic differentiation was observed with the treatment of eBMMMSCs with conditioned medium. The eBMMSCs treated with conditioned medium decreased ROS production, indicating a possible antioxidant defense potential of magnesium release.

Effect of Magnesium on Dentinogenesis of Human Dental Pulp Cells

Introducing therapeutic ions into pulp capping materials has been considered a new approach for enhancing regeneration of dental tissues. However, no studies have been reported on its dentinogenic effects on human dental pulp cells (HDPCs). This study was designed to investigate the effects of magnesium (Mg2+) on cell attachment efficiency, proliferation, differentiation, and mineralization of HDPCs. HDPCs were cultured with 0.5 mM, 1 mM, 2 mM, 4 mM, and 8 mM concentrations of supplemental Mg2+ and 0 mM (control). Cell attachment was measured at 4, 8, 12, 16, and 20 hours. Cell proliferation rate was evaluated at 3, 7, 10, 14, and 21 days. Crystal violet staining was used to determine cell attachment and proliferation rate. Alkaline phosphatase (ALP) activity was assessed using the fluorometric assay at 7, 10, and 14 days. Mineralization of cultures was measured by Alizarin red staining. Statistical analysis was done using multiway analysis of variance (multiway ANOVA) with Wilks' lambda test. Higher cell attachment was shown with 0.5 mM and 1 mM at 16 hours compared to control (P < 0.0001). Cells with 0.5 mM and 1 mM supplemental Mg2+ showed significantly higher proliferation rates than control at 7, 10, 14, and 21 days (P < 0.0001). However, cell proliferation rates decreased significantly with 4 mM and 8 mM supplemental Mg2+ at 14 and 21 days (P < 0.0001). Significantly higher levels of ALP activity and mineralization were observed in 0.5 mM, 1 mM, and 2 mM supplemental Mg2+ at 10 and 14 days (P < 0.0001). However, 8 mM supplemental Mg2+ showed lower ALP activity compared to control at 14 days (P < 0.0001), while 4 mM and 8 mM supplemental Mg2+showed less mineralization compared to control (P < 0.0001). The study indicated that the optimal (0.5-2 mM) supplemental Mg2+ concentrations significantly upregulated HDPCs by enhancing cell attachment, proliferation rate, ALP activity, and mineralization. Magnesium-containing biomaterials could be considered for a future novel dental pulp-capping additive in regenerative endodontics.

The fabrication of a highly efficient hydrogel based on a functionalized double network loaded with magnesium ion and BMP2 for bone defect synergistic treatment

Although the use of bioactive ions and proteins are crucial for bone defect repair, delivering them in a stable and controlled manner remains challenging. To achieve controlled delivery of osteogenic active factor, we developed a novel double network (DN) hydrogel capable of co-delivering Mg²⁺ ions and BMP2 in a controlled localized manner. This DN hydrogel was composed of poly (acrylamide) and chitosan, in which the poly (acrylamide) was cross-linked via covalent bond and the chitosan was grafted using bisphosphonate (BP) to form metal coordination bonds with Mg²⁺ ions. Due to this dynamic dissociation and re-association of the "BP-Mg²⁺" coordination bond, it was possible to deliver Mg²⁺ ions in a stable and controlled manner. Additionally, the obtained DN hydrogel exhibited an effective tensile strength (0.62 MPa), perfect stretchability (973% fracture strain), and good creep and recovery properties due to the dynamic cross-linking effect of "BP-Mg²⁺". Additionally, the hydrogel could synergistically promote the proliferation and differentiation of mouse embryo osteoblast precursor cells (MC3T3-E1 cells) in vitro via the BMP2/Wnt pathway. In the skull defect rat model, this positive delivery government of Mg²⁺ ions and BMP2 synergistically accelerated bone regeneration. In conclusion, this dynamic cross-linked hydrogel containing Mg²⁺ ions established a new platform for the sustained release of osteogenesis factor and accelerated the bone regeneration process.

Impact of exogenous metal ions on peri-implant bone metabolism: a review

The development of effective methods to promote the osseointegration of dental implants by surface modification is an area of intense research in dental materials science. Exogenous metal ions present in the implant and surface modifications are closely related to the bone metabolism around the implant. In the complex oral microenvironment, the release of metal ions caused by continuous corrosion of dental implants has an unfavorable impact on the surrounding tissue, and then affects osseointegration, leading to bad results such as loosening and falling off in the late stage of the implant. Besides, these ions can even be distributed in distant tissues and organs. Currently, surface modification techniques are being developed that involve different processing technologies including the introduction of exogenous metal ions with different properties onto the surface of implants to improve performance. However, most metal elements have some level of biological toxicity and can only be used within a safe concentration range to exert the optimum biological effects on recipients. In this paper, we review the adverse effects of metal ions on osseointegration and highlight the emerging applications for metal elements in improving the performance of dental implants.

Insights into the Role of Magnesium Ions in Affecting Osteogenic Differentiation of Mesenchymal Stem Cells

Bone marrow mesenchymal stem cells (MSCs) are multipotent stem cells with the ability to differentiate into bone-producing cells, which is essential for bone formation. Magnesium biomedical materials, such as biodegradable matters with osteoinductive properties, play a vital role in the osteogenic differentiation of MSCs. International and Chinese studies have shown that magnesium ions, which are produced by biodegradation, mainly achieve this effect by regulating the expression of genes and proteins associated with osteogenesis, activating multiple signal pathways, elevating autophagic activities, and adjusting the pH in the microenvironment. It is of great significance to study the regulatory mechanisms and identify the optimal conditions that how magnesium ions promote osteogenic differentiation of MSCs. In this study, we summarized the regulatory mechanisms noted above.

Regulation of extracellular bioactive cations in bone tissue microenvironment induces favorable osteoimmune conditions to accelerate in situ bone regeneration

The design of orthopedic biomaterials has gradually shifted from “immune-friendly” to “immunomodulatory,” in which the biomaterials are able to modulate the inflammatory response via macrophage polarization in a local immune microenvironment that favors osteogenesis and implant-to-bone osseointegration. Despite the well-known effects of bioactive metallic ions on osteogenesis, how extracellular metallic ions manipulate immune cells in bone tissue microenvironments toward osteogenesis and subsequent bone formation has rarely been studied. Herein, we investigate the osteoimmunomodulatory effect of an extracellular bioactive cation (Mg²⁺) in the bone tissue microenvironment using custom-made poly lactic-co-glycolic acid (PLGA)/MgO-alendronate microspheres that endow controllable release of magnesium ions. The results suggest that the Mg²⁺-controlled tissue microenvironment can effectively induce macrophage polarization from the M0 to M2 phenotype via the enhancement of anti-inflammatory (IL-10) and pro-osteogenic (BMP-2 and TGF-β1) cytokines production. It also generates a favorable osteoimmune microenvironment that facilitates the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells. The in vivo results further verify that a large amount of bony tissue, with comparable bone mineral density and mechanical properties, has been generated at an early post-surgical stage in rat intramedullary bone defect models. This study demonstrates that the concept of in situ immunomodulated osteogenesis can be realized in a controlled magnesium tissue microenvironment.

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Controlled release of Mg²⁺ was achieved by the microfluidic electrosprayed PLGA/MgO-alendronate microspheres.

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PLGA/MgO-alendronate microspheres with satisfied osteoimmunomodulatory properties accelerated bone regeneration in vivo.

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Extracellular Mg²⁺ induced macrophage switch to M2 phenotype with enhanced expressions of IL-10, BMP-2 and TGF-β1.

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Osteoimmune microenvironment favourably upregulated the osteogenic expressions of BMSCs.

Surface Modification of Biodegradable Mg-Based Scaffolds for Human Mesenchymal Stem Cell Proliferation and Osteogenic Differentiation

Magnesium alloys with coatings have the potential to be used for bone substitute alternatives since their mechanical properties are close to those of human bone. However, the surface modification of magnesium alloys to increase the surface biocompatibility and reduce the degradation rate remains a challenge. Here, FHA-Mg scaffolds were made of magnesium alloys and coated with fluorohydroxyapatite (FHA). Human mesenchymal stem cells (hMSCs) were cultured on FHA-Mg scaffolds and cell viability, proliferation, and osteogenic differentiation were investigated. The results showed that FHA-Mg scaffolds display a nano-scaled needle-like structure of aggregated crystallites on their surface. The average Mg²⁺ concentration in the conditioned media collected from FHA-Mg scaffolds (5.8–7.6 mM) is much lower than those collected from uncoated, Mg(OH)₂-coated, and hydroxyapatite (HA)-coated samples (32.1, 17.7, and 21.1 mM, respectively). In addition, compared with hMSCs cultured on a culture dish, cells cultured on FHA-Mg scaffolds demonstrated better proliferation and comparable osteogenic differentiation. To eliminate the effect of osteogenic induction medium, hMSCs were cultured on FHA-Mg scaffolds in culture medium and an approximate 66% increase in osteogenic differentiation was observed three weeks later, indicating a significant effect of the nanostructured surface of FHA-Mg scaffolds on hMSC behaviors. With controllable Mg²⁺ release and favorable mechanical properties, porous FHA-Mg scaffolds have a great potential in cell-based bone regeneration.

Development of biodegradable Zn-1Mg-0.1RE (RE = Er, Dy, and Ho) alloys for biomedical applications

Zinc (Zn) and its alloys are receiving great attention as promising biodegradable materials due to their suitable corrosion resistance, good biocompatibility, and highly desirable biofunctionality. Nevertheless, the low mechanical strength of pure Zn impedes its practical clinical application and there have been calls for further research into the Zn alloys and thermomechanical processes to enhance their mechanical properties and biocompatibility. Here, we report on the alloying efficacy of rare earth elements (REEs) including erbium (Er), dysprosium (Dy), and holmium (Ho) on the microstructure, mechanical properties, corrosion and wear behavior, and in vitro biological properties of Zn-1Mg-0.1RE alloys. Microstructural characterization revealed that the addition of 0.1 wt.% REEs had a significant refining effect on the grain size of the α-Zn matrix and the second phases of the alloys. Alloying of the REEs and hot-rolling effectively improved the mechanical properties due to both precipitation strengthening of the second phases of ErZn₅, DyZn₅, and Ho₂Zn₁₇ and grain-refinement strengthening. The highest ultimate tensile strength of 259.4 MPa and yield strength of 234.8 MPa with elongation of 16.8% were achieved in the hot-rolled Zn-1Mg-0.1Ho. Alloying of REEs also improved the wear and corrosion resistance, and slowed down the degradation rate in Hanks' solution. Zn-1Mg-0.1Er showed the highest cytocompatibility of MC3T3-E1 cells cultured directly on the alloy surface and of MG-63 cells cultured in the alloy extract. Zn-1Mg-0.1Dy showed the best anticoagulant property among all the alloys. Overall, these Zn-1Mg-0.1RE (Er, Dy, and Ho) alloys can be considered promising biodegradable metallic materials for orthopedic applications.

Exposure to high levels of magnesium disrupts bone mineralization in vitro and in vivo

Background

The removal of permanent internal fixation devices by secondary surgery could be avoided if these devices were made of degradable magnesium and magnesium alloys. Before such implants can be used clinically, however, the biological effect of magnesium exposure on surrounding bone must be evaluated. Previous studies have focused on bone formation; few have examined the effects of magnesium on the bone quality that affect many biomechanical properties.

Methods

Using bone quality parameters, we analyzed in vivo changes in bone properties and biomechanics after exposure to locally high levels of magnesium.

Results

Local bone mineralization was significantly disrupted following exposure to a porous rod of pure magnesium. Normal crystal formation and crystallinity were inhibited and the mineral-to-matrix ratio decreased. These results were consistent with those of in vitro experiments, in which high levels of magnesium inhibited mineral deposition by mesenchymal stem cells (MSCs) but increased alkaline phosphatase (ALP) expression. The same mineralization inhibition was observed around magnesium implants via micro-computerized tomography (micro-CT) and von Kossa staining. Such reduced bone quality around degrading magnesium rods could negatively impact bone biomechanics.

Conclusions

This study showed that exposure to the local high magnesium levels that arise from rapidly degrading magnesium devices may significantly disrupt bone mineralization and negatively impact bone biomechanics.

Stem cell plasticity and regenerative potential regulation through Ca2+-mediated mitochondrial nuclear crosstalk

The multi-lineage differentiation potential is one of the prominent mechanisms through which stem cells can repair damaged tissues. The regenerative potential of stem cells is the manifestation of several changes at the structural and molecular levels in stem cells that are regulated through intricate mitochondrial-nuclear interactions maintained by Ca²⁺ ion signaling. Despite the exhilarating evidences strengthening the versatile and indispensible role of Ca²⁺ in regulating mitochondrial-nuclear interactions, the extensive details of signaling mechanisms remains largely unexplored. In this review we have discussed the effect of Ca²⁺ ion mediated mitochondrial-nuclear interactions participating in stem plasticity and its regenerative potential.

Bio-inspired biomaterial Mg-Zn-Ca: a review of the main mechanical and biological properties of Mg-based alloys

The toxicity of alloying elements in magnesium alloys used for biomedical purposes is an interesting and innovative subject, due to the great technological advances that would result from their application in medical devices (MDs) in traumatology. Recently promising results have been published regarding the rates of degradation and mechanical integrity that can support Mg alloys; this has led to an interest in understanding the toxicological features of these emerging biomaterials. The growing interest of different segments of the MD market has increased the determination of different research groups to clarify the behavior of alloying elements in vivo. This review covers the influence of the alloying elements on the body, the toxicity of the elements in Mg-Zn-Ca, as well as the mechanical properties, degradation, processes of obtaining the alloy, medical approaches and future perspectives on the use of the Mg in the manufacture of MDs for various medical applications.

In vitro bioactivity of AH plus with the addition of nano-magnesium hydroxide

Background

AH Plus (AH) has been widely used as a root canal sealer in the endodontic field due to its superior physicochemical properties. However, clinical application of AH is limited due to its weak bioactivity.

Methods

In this study, we have developed an AH cement containing nano-magnesium hydroxide (NMH) as an additive to enhance the bioactivity of AH. The NMH can neutralize pH and facilitate bone formation. The objective of this study was to evaluate the effects of NMH and modified AH on osteoblasts behavior in vitro. The CCK-8, alkaline phosphatase (ALP) staining, and real-time polymerase chain reaction (PCR) assays were used to assess the proliferation and differentiation of MC3T3-E1 cells, respectively. The adhesion and spreading of MC3T3-E1 cells were investigated in vitro by scanning electron microscopy (SEM). Meanwhile, the flow and magnesium ion release of the modified AH was also concerned.

Results

In vitro cell assays further showed that the addition of NMH into AH cement, which was denoted as modified AH (especially AH+3%NMH), could effectively improve the proliferation and osteogenic differentiation of MC3T3-E1 cells.

Conclusions

Taken all together, we believe that the modified AH samples (especially AH+3%NMH) have outstanding biocompatibility and osteogenic properties and may have great potential in endodontic field.

The relative effects of Ca and Mg ions on MSC osteogenesis in the surface modification of microrough Ti implants

Purpose

Calcium (Ca) and magnesium (Mg) ions have been used as promising bioactive ions in the surface chemistry modification of titanium (Ti) bone implants to increase bone regeneration capacity. However, it is not clear which (Ca or Mg) plays the more important role in the early osteogenic differentiation of mesenchymal stem cells (MSCs) when applied to the surface of commercially available microstructured Ti implants. This study investigated the relative effect of these two ions on the early osteogenic functionality of primary mouse bone marrow MSCs in order to obtain insights into the surface design of Ti implants with enhanced early osteogenic capacity.

Methods and results

Wet chemical treatment was performed to modify a microrough Ti implant surface using Ca or Mg ions. Both the Ca and Mg-incorporated surfaces accelerated early cellular events and the subsequent osteogenic differentiation of MSCs compared with an unmodified microrough Ti surface. Surface Mg modification exhibited a more potent osteoblast differentiation-promoting effect than the Ca modification. Surface Mg incorporation markedly inhibited the phosphorylation of β-catenin.

Conclusion

These results indicate that alteration of the surface chemistry of microstructured Ti implants by wet chemical treatment with Mg ions exerts a more effect on promoting the early osteogenic differentiation of MSCs than Ca ions by enhancing early cellular functions, including focal adhesion development and stabilization of intracellular β-catenin.

High concentration magnesium inhibits extracellular matrix calcification and protects articular cartilage via Erk/autophagy pathway

The significant cytopathological changes of osteoarthritis are chondrocyte hypertrophy, proteoglycan loss, extracellular matrix (ECM) calcification, and terminally, the replacement of cartilage by bone. Meanwhile, magnesium ion (Mg²⁺ ), as the second most abundant divalent cation in the human body, has been proved to inhibit the ECM calcification of hBMSCs (human bone marrow stromal cells), hVSMCs (Human vascular smooth muscle cells), and TDSCs (tendon-derived stem cells) in vitro studies. The ATDC5 cell line, which holds chondrocyte characteristics, was used in this study as an in vitro subject. We found that Mg²⁺ can efficiently suppress the ECM calcification and downregulate both hypertrophy and matrix metalloproteinase-related genes. Meanwhile, Mg²⁺ inhibits the formation of autophagy by inhibiting Erk phosphorylation signaling and lowers the expression of LC3, and eventually effectively reduces the formation of ECM calcification in vitro. In this study, we also used destabilization of the medial meniscus (DMM)-induced osteoarthritis (OA) animal model to further confirm the protective effect of Mg²⁺ on articular cartilage. Compared with the control group (saline-injected), continuous intra-articular magnesium chloride (MgCl₂ ) injection can significantly alleviate the severity of cartilage calcification in OA animal model. Immunofluorescence staining also revealed that saline-injected DMM group had a higher positive rate of LC3 expression in cartilage chondrocytes, compared with MgCl₂ -injected DMM group. In general, Mg²⁺ can significantly downregulate the hypertrophic gene Runx2, MMP13, and Col10α1, upregulate the chondrogenic genes Sox9 and Col1α1, inhibit the Erk phosphorylation signaling, reduce the expression of autophagy protein LC3, and effectively inhibit the ECM calcification of ATDC5. In vivo study also proved that intra-articular injection of Mg²⁺ protected knee cartilage by inhibiting the autophagy formation.

Magnesium Is a Key Regulator of the Balance between Osteoclast and Osteoblast Differentiation in the Presence of Vitamin D₃

Magnesium (Mg) is crucial for bone health. Low concentrations of Mg inhibit the activity of osteoblasts while promoting that of osteoclasts, with the final result of inducing osteopenia. Conversely, little is known about the effects of high concentrations of extracellular Mg on osteoclasts and osteoblasts. Since the differentiation and activation of these cells is coordinated by vitamin D₃ (VD3), we investigated the effects of high extracellular Mg, as well as its impact on VD3 activity, in these cells. U937 cells were induced to osteoclastic differentiation by VD3 in the presence of supra-physiological concentrations (>1 mM) of extracellular Mg. The effect of high Mg concentrations was also studied in human bone-marrow-derived mesenchymal stem cells (bMSCs) induced to differentiate into osteoblasts by VD3. We demonstrate that high extra-cellular Mg levels potentiate VD3-induced osteoclastic differentiation, while decreasing osteoblastogenesis. We hypothesize that Mg might reprogram VD3 activity on bone remodeling, causing an unbalanced activation of osteoclasts and osteoblasts.

Effect of High- and Low-Molecular-Weight Hyaluronic-Acid-Functionalized-AZ31 Mg and Ti Alloys on Proliferation and Differentiation of Osteoblast Cells

The quality of patient care has increased dramatically in recent years because of the development of lightweight orthopedic metal implants. The success of these orthopedic implants may be compromised by impaired cytocompatibility and osteointegration. Biomimetic surface engineering of metal implants using biomacromolecules including hyaluronic acid (HA) has been used an effective approach to provide conditions favorable for the growth of bone forming cells. To date, there have been limited studies on osteoblasts functions in response to metal substrates modified with the hyaluronic acid of different molecular weight for orthopedic applications. In this study, we evaluated the osteoblasts functions such as adhesion, proliferation, and differentiation in response to high- and low-molecular-weight HA (denoted as h-HA and l-HA, respectively) functionalized on Ti (h-HA-Ti and l-HA-Ti substrates, respectively) and corrosion-resistant silane coated-AZ31 Mg alloys (h-HA-AZ31 and l-HA-AZ31). The DNA quantification study showed that adhesion and proliferation of osteoblasts were significantly decreased by h-HA immobilized on Ti or AZ31 substrates when compared to low-molecular-weight counterpart over a period of 14 days. On the contrary, h-HA significantly increased the osteogenic differentiation of osteoblast over l-HA, as confirmed by the enhanced expression of ALP, total collagen, and mineralization of extracellular matrix. In particular, the h-HA-AZ31 substrates greatly enhanced the osteoblast differentiation among tested samples (l-HA-AZ31, l-HA-Ti, h-HA-Ti, and Ti alone), which is ascribed to the osteoinductive activity of h-HA, relatively up-regulated intracellular Ca²⁺ ([Ca²⁺]_i) and Mg²⁺ ([Mg²⁺]_i) concentrations as well as the alkalization of the cell culture medium. This study suggesting that HA of appropriate molecular weight can be successfully used to modify the surface of metal implants for orthopedic applications.

High Magnesium Corrosion Rate has an Effect on Osteoclast and Mesenchymal Stem Cell Role During Bone Remodelling

The aim of this study was to gain an understanding on the collective cellular effects of magnesium (Mg) corrosion products on the behaviour of cells responsible for bone formation and remodelling. The response of mesenchymal stem cells (MSCs) and osteoclast cells to both soluble (Mg ions) and insoluble (granule) corrosion products were recapitulated in vitro by controlling the concentration of the corrosion products. Clearance of corrosion granules by MSCs was also inspected by TEM analysis at sub-cellular level. The effect of Mg corrosion products varied depending on the state of differentiation of cells, concentration and length of exposure. The presence of the corrosion products significantly altered the cells' metabolic and proliferative activities, which further affected cell fusion/differentiation. While cells tolerated higher than physiological range of Mg concentration (16 mM), concentrations below 10 mM were beneficial for cell growth. Furthermore, MSCs were shown to contribute to the clearance of intercellular corrosion granules, whilst high concentrations of corrosion products negatively impacted on osteoclast progenitor cell number and mature osteoclast cell function.

Applications of Metals for Bone Regeneration

The regeneration of bone tissue is the main purpose of most therapies in dental medicine. For bone regeneration, calcium phosphate (CaP)-based substitute materials based on natural (allo- and xenografts) and synthetic origins (alloplastic materials) are applied for guiding the regeneration processes. The optimal bone substitute has to act as a substrate for bone ingrowth into a defect, as well as resorb in the time frame needed for complete regeneration up to the condition of restitution ad integrum. In this context, the modes of action of CaP-based substitute materials have been frequently investigated, where it has been shown that such materials strongly influence regenerative processes such as osteoblast growth or differentiation and also osteoclastic resorption due to different physicochemical properties of the materials. However, the material characteristics needed for the required ratio between new bone tissue formation and material degradation has not been found, until now. The addition of different substances such as collagen or growth factors and also of different cell types has already been tested but did not allow for sufficient or prompt application. Moreover, metals or metal ions are used differently as a basis or as supplement for different materials in the field of bone regeneration. Moreover, it has already been shown that different metal ions are integral components of bone tissue, playing functional roles in the physiological cellular environment as well as in the course of bone healing. The present review focuses on frequently used metals as integral parts of materials designed for bone regeneration, with the aim to provide an overview of currently existing knowledge about the effects of metals in the field of bone regeneration.

High magnesium prevents matrix vesicle-mediated mineralization in human bone marrow-derived mesenchymal stem cells via mitochondrial pathway and autophagy

Magnesium, as a physiological calcium antagonist, plays a vital role in the bone metabolism and the balance between magnesium and calcium is crucial in bone physiology. We recently demonstrated that matrix mineralization in human bone marrow-derived mesenchymal stem cells (hBMSCs) can be suppressed by high Mg²⁺ . However, a complete understanding of the mechanisms involved still remains to be elucidated. As mitochondrial calcium phosphate granules depletion manifests concurrently with the appearance of matrix vesicles (MVs) and autophagy are associated with matrix mineralization, we studied the effect of high extracellular Mg²⁺ on these pathways. Our results first demonstrated that high Mg²⁺ has a significant inhibitory effect on the generalization of extracellular mineral aggregates and the expression of collagen 1 along which the mineral crystals grow. Transmission electron microscope results showed that less amount of MVs were observed inside hBMSCs treated with high Mg²⁺ and high Mg²⁺ inhibited the release of MVs. In addition, high Mg²⁺ significantly suppressed mitochondrial Ca²⁺ accumulation. Autophagy is promoted as a response to osteogenesis of hBMSCs. High Mg²⁺ inhibited the level of autophagy upon osteogenesis and autophagy inhibitor 3-MA significantly suppressed mineralization. Exogenous ATP can reverse the inhibitory effect of high Mg²⁺ by increasing the level of autophagy. Taken together, our results indicate that high Mg²⁺ may modulate MVs-mediated mineralization via suppressing mitochondrial Ca²⁺ intensity and regulates autophagy of hBMSCs upon osteogenesis, resulting in decreased extracellular mineralized matrix deposition. Our results contribute to the understanding of the role of magnesium homeostasis in osteoporosis and the design of magnesium alloys.

ATP-induced Ca2+-signalling mechanisms in the regulation of mesenchymal stem cell migration

The ability of cells to migrate to the destined tissues or lesions is crucial for physiological processes from tissue morphogenesis, homeostasis and immune responses, and also for stem cell-based regenerative medicines. Cytosolic Ca²⁺ is a primary second messenger in the control and regulation of a wide range of cell functions including cell migration. Extracellular ATP, together with the cognate receptors on the cell surface, ligand-gated ion channel P2X receptors and a subset of G-protein-coupled P2Y receptors, represents common autocrine and/or paracrine Ca²⁺ signalling mechanisms. The P2X receptor ion channels mediate extracellular Ca²⁺ influx, whereas stimulation of the P2Y receptors triggers intracellular Ca²⁺ release from the endoplasmic reticulum (ER), and activation of both type of receptors thus can elevate the cytosolic Ca²⁺ concentration ([Ca²⁺]_c), albeit with different kinetics and capacity. Reduction in the ER Ca²⁺ level following the P2Y receptor activation can further induce store-operated Ca²⁺ entry as a distinct Ca²⁺ influx pathway that contributes in ATP-induced increase in the [Ca²⁺]_c. Mesenchymal stem cells (MSC) are a group of multipotent stem cells that grow from adult tissues and hold promising applications in tissue engineering and cell-based therapies treating a great and diverse number of diseases. There is increasing evidence to show constitutive or evoked ATP release from stem cells themselves or mature cells in the close vicinity. In this review, we discuss the mechanisms for ATP release and clearance, the receptors and ion channels participating in ATP-induced Ca²⁺ signalling and the roles of such signalling mechanisms in mediating ATP-induced regulation of MSC migration.

Knockdown of SLC41A1 magnesium transporter promotes mineralization and attenuates magnesium inhibition during osteogenesis of mesenchymal stromal cells

BACKGROUND

Magnesium is essential for numerous physiological functions. Magnesium exists mostly in bone and the amount is dynamically regulated by skeletal remodeling. Accelerating bone mass loss occurs when magnesium intake is insufficient; whereas high magnesium could lead to mineralization defects. However, the underlying magnesium regulatory mechanisms remain elusive. In the present study, we investigated the effects of high extracellular magnesium concentration on osteogenic differentiation of mesenchymal stromal/stem cells (MSCs) and the role of magnesium transporter SLC41A1 in the mineralization process.

METHODS

Murine MSCs derived from the bone marrow of BALB/c mouse or commercially purchased human MSCs were treated with osteogenic induction medium containing 5.8 mM magnesium chloride and the osteogenic differentiation efficiency was compared with that of MSCs in normal differentiation medium containing 0.8 mM magnesium chloride by cell morphology, gene expression profile of osteogenic markers, and Alizarin Red staining. Slc41a1 gene knockdown in MSCs was performed by siRNA transfection using Lipofectamine RNAiMAX, and the differentiation efficiency of siRNA-treated MSCs was also assessed.

RESULTS

High concentration of extracellular magnesium ion inhibited mineralization during osteogenic differentiation of MSCs. Early osteogenic marker genes including osterix, alkaline phosphatase, and type I collagen were significantly downregulated in MSCs under high concentration of magnesium, whereas late marker genes such as osteopontin, osteocalcin, and bone morphogenetic protein 2 were upregulated with statistical significance compared with those in normal differentiation medium containing 0.8 mM magnesium. siRNA treatment targeting SLC41A1 magnesium transporter, a member of the solute carrier family with a predominant Mg2+ efflux system, accelerated the mineralization process and ameliorated the inhibition of mineralization caused by high concentration of magnesium. High concentration of magnesium significantly upregulated Dkk1 gene expression and the upregulation was attenuated after the Slc41a1 gene was knocked down. Immunofluorescent staining showed that Slc41a1 gene knockdown promoted the translocation of phosphorylated β-catenin into nuclei. In addition, secreted MGP protein was elevated after Slc41a1 was knocked down.

CONCLUSIONS

High concentration of extracellular magnesium modulates gene expression of MSCs during osteogenic differentiation and inhibits the mineralization process. Additionally, we identified magnesium transporter SLC41A1 that regulates the interaction of magnesium and MSCs during osteogenic differentiation. Wnt signaling is suggested to be involved in SLC41A1-mediated regulation. Tissue-specific SLC41A1 could be a potential treatment for bone mass loss; in addition, caution should be taken regarding the role of magnesium in osteoporosis and the design of magnesium alloys for implantation.

In vivo assessment of a new multifunctional coating architecture for improved Mg alloy biocompatibility

Magnesium alloys are regarded as potential biodegradable load-bearing biomaterials for orthopedic applications due to their physico-chemical and biomechanical properties. However, their clinical applicability is restricted by their high degradation rate, which limits the physiological reconstruction of the neighbouring tissues. In this work, a multifunctional coating architecture was developed on an AZ31 alloy by conjoining an anodization process with the deposition of a polymeric-based layer consisting of polyether imine reinforced with hydroxyapatite nanoparticles, aiming at improved control of the corrosion activity and biological performance of the Mg substrate. Anodization and coating protocols were evaluated either independently or combined for corrosion resistance and biological behaviour, i.e. the irritation potential and angiogenic capability within a chicken chorioallantoic membrane assay, and bone tissue response following tibia implantation within a rabbit model. Electrochemical impedance spectroscopy (EIS) analysis showed that coated Mg constructs, particularly anodized plus coated with AZ31, exhibited excellent stability compared to the anodized alloy and, particularly, to the bare AZ31. Microtomographic evaluation of the implanted samples correlated with these degradation results. Mg constructs displayed a non-irritating behaviour, and were associated with high levels of vascular ingrowth. Bone ingrowth neighbouring the implanted constructs was observed for all samples, with coated and anodized plus coated samples presenting the highest bone formation. Gene expression analysis suggested that the enhanced bone tissue formation was associated with the boost in osteogenic activity through Runx2 upregulation, following the activation of PGC-1α/ERRα signaling. Overall, the developed multifunctional coatings appear to be a promising strategy to obtain safe and bioactive biodegradable Mg-based implants with potential applications within bone tissue.

Magnesium inhibits the calcification of the extracellular matrix in tendon-derived stem cells via the ATP-P2R and mitochondrial pathways

Tendon calcification has been widely regarded by researchers to result from the osteogenic differentiation of Tendon-Derived Stem Cells (TDSCs) and ectopic mineralization caused by the calcification of cellular matrix. Recent studies have revealed a correlation between the Mg(2+)/Ca(2+) balance and the degeneration or calcification of tendon tissues. Furthermore, the ATP-P2X/P2Y receptor pathway has been shown to play a decisive role in the process of calcification, with calcium exportation from mitochondria and calcium oscillations potentially representing the cohesive signal produced by this pathway. Our previous study demonstrated that matrix calcification is inhibited by magnesium. In this study, we examined the effects of extracellular Mg(2+) on the deposition of calcium phosphate matrix and cellular pathways in TDSCs. The suppression of the export of calcium from mitochondria has also been detected. We found that a high concentration of extracellular Mg(2+) ([Mg(2+)]e) inhibited the mineralization of the extracellular matrix in TDSCs and that 100 μM ATP reversed this inhibitory effect in vitro. In addition, the spontaneous release of ATP was inhibited by high [Mg(2+)]e levels. A high [Mg(2+)]e suppressed the expression of P2X4, P2X5 and P2X7 and activated the expression of P2Y1, P2Y2, P2Y4 and P2Y14. The interaction between Mg(2+) and Ca(2+) is therefore contradictory, Mg(2+) inhibits mitochondrial calcium concentrations, meanwhile it reverses the opening of mPTP that is induced by Ca(2+). JC-1 staining verified the protective effect of Mg(2+) on mitochondrial membrane potential and the decrease induced by Ca(2+). Taken together, these results indicate that high [Mg(2+)]e interferes with the expression of P2 receptors, resulting in decreased extracellular mineralization. The balance between Mg(2+) and Ca(2+) influences mitochondrial calcium exportation and provides another explanation for the mechanism underlying matrix calcification in TDSCs.

A preliminary study for novel use of two Mg alloys (WE43 and Mg3Gd)

In this study, two types of magnesium alloys (WE43 and Mg3Gd) were compared with Heal-All membrane (a biodegradable membrane used in guided bone regeneration) in vitro to determine whether the alloys could be used as biodegradable membranes. Degradation behavior was assessed using immersion testing with simulated body fluid (SBF). Microstructural characteristics before and after immersion were evaluated through scanning electron microscopy, and degradation products were analyzed with energy dispersive spectrometry (EDS). To evaluate the biocompatibility of the three types of materials, we performed cytotoxicity, adhesion, and mineralization tests using human osteoblast-like MG63 cells. Immersion testing results showed no significant difference in degradation rate between WE43 and Mg3Gd alloys. However, both Mg alloys corroded faster than the Heal-All membrane, with pitting corrosion as the main corrosion mode for the alloys. Degradation products mainly included P- and Ca-containing apatites on the surface of WE43 and Mg3Gd, whereas these apatites were rarely detected on the surface of the Heal-All membrane. All three type of materials exhibited good biocompatibility. In the mineralization experiment, the alkaline phosphatase (ALP) activity of 10 % Mg3Gd extract was significantly higher than the extracts of the two other materials and the negative control. This study highlighted the potential of these Mg-REE alloys for uses in bone regeneration and further studies and refinements are obviously required.

Role of Magnesium Transporter Subtype 1 (MagT1) in the Osteogenic Differentiation of Rat Bone Marrow Stem Cells

In the present study, we investigated the role of magnesium transporter subtype 1 (MagT1), a selective Mg transporter protein, in the osteogenic differentiation of rat bone marrow stem cells (rBMSCs). Osteogenic differentiation was monitored by the expressions of alkaline phosphatase (ALP), osteocalcin (OCN), collagen-1 (COL-1) and runt-related transcription factor 2 (RUNX2), and extracellular matrix mineralization of rBMSCs. The expression of MagT1 increased with osteogenic differentiation of rBMSCs, suggesting the importance of intracellular Mg homeostasis to cell differentiation. Alteration of intracellular Mg homeostasis by culture condition with low extracellular Mg significantly reduced the osteogenic differentiation markers ALP, OCN, COL-1, and RUNX2 gene expressions. MagT1 knockdown during the differentiation period also reduced osteogenic differentiation and the extent of matrix mineralization of rBMSCs. In conclusion, our results indicate that Mg and MagT1 play an important role in osteogenic differentiation of rBMSCs and may be involved in the bone regeneration.

Purinergic and Store-Operated Ca(2+) Signaling Mechanisms in Mesenchymal Stem Cells and Their Roles in ATP-Induced Stimulation of Cell Migration

ATP is an extrinsic signal that can induce an increase in the cytosolic Ca(2+) level ([Ca(2+) ]c ) in mesenchymal stem cells (MSCs). However, the cognate intrinsic mechanisms underlying ATP-induced Ca(2+) signaling in MSCs is still contentious, and their importance in MSC migration remains unknown. In this study, we investigated the molecular mechanisms underlying ATP-induced Ca(2+) signaling and their roles in the regulation of cell migration in human dental pulp MSCs (hDP-MSCs). RT-PCR analysis of mRNA transcripts and interrogation of agonist-induced increases in the [Ca(2+) ]c support that P2X7, P2Y1 , and P2Y11 receptors participate in ATP-induced Ca(2+) signaling. In addition, following P2Y receptor activation, Ca(2+) release-activated Ca(2+) Orai1/Stim1 channel as a downstream mechanism also plays a significant role in ATP-induced Ca(2+) signaling. ATP concentration-dependently stimulates hDP-MSC migration. Pharmacological and genetic interventions of the expression or function of the P2X7, P2Y1 and P2Y11 receptors, and Orai1/Stim1 channel support critical involvement of these Ca(2+) signaling mechanisms in ATP-induced stimulation of hDP-MSC migration. Taken together, this study provide evidence to show that purinergic P2X7, P2Y1 , and P2Y11 receptors and store-operated Orai1/Stim1 channel represent important molecular mechanisms responsible for ATP-induced Ca(2+) signaling in hDP-MSCs and activation of these mechanisms stimulates hDP-MSC migration. Such information is useful in building a mechanistic understanding of MSC homing in tissue homeostasis and developing more efficient MSC-based therapeutic applications. Stem Cells 2016;34:2102-2114.

Unraveling the role of Mg(++) in osteoarthritis

Mg(++) is widely involved in human physiological processes that may play key roles in the generation and progression of diseases. Osteoarthritis (OA) is a complex joint disorder characterized by articular cartilage degradation, abnormal mineralization and inflammation. Magnesium deficiency is considered to be a major risk factor for OA development and progression. Magnesium deficiency is active in several pathways that have been implicated in OA, including increased inflammatory mediators, cartilage damage, defective chondrocyte biosynthesis, aberrant calcification and a weakened effect of analgesics. Abundant in vitro and in vivo evidence in animal models now suggests that the nutritional supplementation or local infiltration of Mg(++) represent effective therapies for OA. The goal of this review is to summarize the current understanding of the role of Mg(++) in OA with particular emphasis on the related molecular mechanisms involved in OA progression.

Enhanced osteoblast differentiation and osseointegration of a bio-inspired HA nanorod patterned pore-sealed MgO bilayer coating on magnesium

The osteogenetic capability of Mg was significantly enhanced by a bio-inspired hydroxyapatite (HA) nanorod patterned pore-sealed MgO bilayer coating.

The Wnt11 Signaling Pathway in Potential Cellular EMT and Osteochondral Differentiation Progression in Nephrolithiasis Formation

The molecular events leading to nephrolithiasis are extremely complex. Previous studies demonstrated that calcium and transforming growth factor-β1 (TGF-β1) may participate in the pathogenesis of stone formation, but the explicit mechanism has not been defined. Using a self-created genetic hypercalciuric stone-forming (GHS) rat model, we observed that the increased level of serous/uric TGF-β1 and elevated intracellular calcium in primary renal tubular epithelial cells (PRECs) was associated with nephrolithiasis progression in vivo. In the setting of high calcium plus high TGF-β1 in vitro, PRECs showed great potential epithelial to mesenchymal transition (EMT) progression and osteochondral differentiation properties, representing the multifarious increased mesenchymal and osteochondral phenotypes (Zeb1, Snail1, Col2A1, OPN, Sox9, Runx2) and decreased epithelial phenotypes (E-cadherin, CK19) bythe detection of mRNAs and corresponding proteins. Moreover, TGF-β-dependent Wnt11 knockdown and L-type Ca²⁺ channel blocker could greatly reverse EMT progression and osteochondral differentiation in PRECs. TGF-β1 alone could effectively promote EMT, but it had no effect on osteochondral differentiation in NRK cells (Rat kidney epithelial cell line). Stimulation with Ca²⁺ alone did not accelerate differentiation of NRK. Co-incubation of extracellular Ca²⁺ and TGF-β1 synergistically promotes EMT and osteochondral differentiation in NRK control cells. Our data supplied a novel view that the pathogenesis of calcium stone development may be associated with synergic effects of TGF-β1 and Ca²⁺, which promote EMT and osteochondral differentiation via Wnt11 and the L-type calcium channel.