Magnesium deficiency results in an increased formation of osteoclasts

The Biological Effects of Magnesium-Based Implants on the Skeleton and Their Clinical Implications in Orthopedic Trauma Surgery

Magnesium (Mg)-based implants have evolved as a promising innovation in orthopedic trauma surgery, with the potential to revolutionize the treatment of bone diseases, including osteoporotic fractures and bone defects. Available clinical studies mostly show excellent patient outcomes of resorbable Mg-based implants, without the need for subsequent implant removal. However, the occurrence of radiolucent zones around Mg-based implants seems to be a noticeable drawback for a more widespread clinical use. Mechanistically, both in vivo and in vitro studies demonstrated beneficial effects on the formation of new bone, a unique characteristic of Mg-based implants. In this regard, Mg has been shown to exert pleiotropic functions on osteogenic differentiation and migration of osteoblasts and their precursors. Additionally, collective evidence suggests that Mg-based implants promote angiogenesis in newly formed bone and exert immunomodulatory effects in the bone microenvironment. Likewise, Mg-based implants and their degradation products were shown to inhibit bone resorption by impairing osteoclastogenesis. The purpose of this review is to provide a state-of-the-art summary of the clinical and basic science evidence regarding the performance of currently used Mg-based implants. In addition to the status of in vivo and in vitro research and clinical applications, future challenges and perspectives of Mg-based orthopedic implants are discussed.

Magnesium biology

Magnesium (Mg2+) is essential for energy metabolism, muscle contraction and neurotransmission. As part of the Mg-ATP complex, it is involved in over 600 enzymatic reactions. Serum Mg2+ levels are tightly regulated between 0.7 and 1.1 mmol/L by interplay of intestinal absorption and renal excretion. In the small intestine, Mg2+ is absorbed paracellularly via claudin-2 and -12. In the colon, transcellular absorption of Mg2+ is facilitated by TRPM6/7 and CNNM4. In the kidney, the proximal tubule reabsorbs only 20% of the filtered Mg2+. The majority of the filtered Mg2+ is reabsorbed in the thick ascending limb, where the lumen-positive transepithelial voltage drives paracellular transport via claudin-16/-19. Fine-tuning of Mg2+ reabsorption is achieved in the distal convoluted tubule (DCT). Here, TRPM6/7 tetramers facilitate apical Mg2+ uptake, which is hormonally regulated by insulin and epidermal growth factor. Basolateral Mg2+ extrusion is Na+ dependent and achieved by CNNM2 and/or SLC41A3. Hypomagnesemia (serum Mg2+ <0.7 mmol/L) develops when intestinal and/or renal Mg2+ (re)absorption is disturbed. Common causes include alcoholism, type 2 diabetes mellitus and the use of pharmacological drugs, such as proton-pump inhibitors, calcineurin inhibitors and thiazide diuretics. Over the last decade, research on rare genetic and acquired Mg2+ disorders have identified Mg2+ channel and transporter activity, DCT length, mitochondrial function and autoimmunity as mechanisms explaining hypomagnesemia. Classically, treatment of hypomagnesemia depended on oral or intravenous Mg2+ supplementation. Recently, prebiotic dietary fibers and sodium-glucose cotransporter 2 inhibitors have been proposed as promising new therapeutic pathways to treat hypomagnesemia.

Magnesium-Doped Hydroxyapatite Nanofibers for Medicine Applications: Characterization, Antimicrobial Activity, and Cytotoxicity Study

Magnesium-doped hydroxyapatite (HAp-Mg) nanofibers show promise for medical applications due to their structural similarity to bone minerals and enhanced biological properties, such as improved biocompatibility and antimicrobial activity. This study synthesized HAp-Mg nanofibers using a microwave-assisted hydrothermal method (MAHM) to evaluate their cytotoxicity, biocompatibility, and antimicrobial efficacy compared to commercial hydroxyapatite (HAp). Characterization through X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR) confirmed the successful incorporation of magnesium, producing high-purity, crystalline nanofibers with hexagonal morphology. Rietveld refinement showed slight lattice parameter shortening, indicating Mg2+ ion integration. Cell viability assays (MTT and AlamarBlue) revealed a significant increase in fibroblast proliferation with 2% and 5% HAp-Mg concentrations compared to controls (p < 0.05), demonstrating non-cytotoxicity and enhanced biocompatibility. Antimicrobial tests (disk diffusion method, 100 µg/mL) showed that HAp-Mg had strong antibacterial effects against Gram-positive and Gram-negative bacteria and moderate antifungal activity against Candida albicans. In contrast, commercial HAp showed no antimicrobial effects. These results suggest HAp-Mg nanofibers have significant advantages as biomaterials for medical applications, particularly in preventing implant-related infections and supporting further clinical development.

Modeling calcium and magnesium balance: Regulation by calciotropic hormones and adaptations under varying dietary intake

Magnesium (Mg2+) is crucial for several cellular and physiological processes and is tightly regulated due to health risks associated with imbalances. Mg2+, calcium (Ca2+), parathyroid hormone, and vitamin D3 are tightly coupled, ensuring proper bone metabolism and intestinal and renal absorption of Mg2+ and Ca2+. While several Ca2+ homeostasis models exist, no computational model has been developed to study Mg2+ homeostasis. We developed a computational model of Mg2+ homeostasis in male rats, integrating it with an existing Ca2+ homeostasis model, to understand the interconnected physiological processes regulating their homeostasis. We then analyzed adaptations in these interconnected processes under (1) dietary Mg2+ deficiency, (2) low/high dietary Ca2+ with Mg2+ deficiency, and (3) vitamin D3 deficiency. Model simulations predicted severe hypomagnesemia and mild hypocalcemia with significant dietary Mg2+ deficiency. Low dietary Ca2+ improved, while high dietary Ca2+ worsened Mg2+ deficiency. Finally, vitamin D3 deficiency caused severe hypocalcemia, with minimal impact on Mg2+ homeostasis.

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

BACKGROUND

Critical bone defects pose a significant challenge for orthopedic surgeons. Autologous bone grafting is the golden standard. However, it is hindered by issues such as donor site morbidity and limited availability. Commercially available artificial bone grafts may encounter challenges in properly integrating the surrounding bone tissue, potentially leading to delayed or incomplete healing. Furthermore, magnesium deficiency has been shown to negatively affect localized angiogenesis and bone repair. As a result, creating a synthetic biomaterial that includes magnesium could serve as an excellent bone substitute. The study aims to evaluate and test the morphological, mechanical, and biological properties of a calcium phosphate cement (CPC) sponge composed of tetracalcium phosphate (TTCP) and monocalcium phosphate monohydrate (MCPM).

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 min 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.

Effect of magnesium oxide nanoparticles and LED irradiation on the viability and differentiation of human stem cells of the apical papilla

PURPOSE

Currently, regenerative endodontic treatments are gaining more and more attention, and stem cells play a significant role in these treatments. In order to enhance stem cell proliferation and differentiation, a variety of methods and materials have been used. The purpose of this study was to determine the effects of magnesium oxide nanoparticles and LED irradiation on the survival and differentiation of human stem cells from apical papilla.

METHODS

The MTT test was used to measure the cell survival of SCAPs that had been exposed to different concentrations of magnesium oxide nanoparticles after 24 and 48 h, and the concentration with the highest cell survival rate was picked for further studies. The cells were classified into four distinct groups based on their treatment: (1) control, which received no exposure, (2) exposure to magnesium oxide nanoparticles, (3) exposure to light emitting diode (LED) irradiation (635 nm, 200 mW/cm2) for 30 s, (4) exposure simultaneously with magnesium oxide nanoparticles and LED irradiation. A green approach was employed to synthesize magnesium oxide nanoparticles. Quantitative real time PCR was used to measure the gene expression of osteo/odontogenic markers such as BSP, DSPP, ALP and DMP1 in all four groups after treatment, and Alizarin red S staining (ARS) was used to determine the osteogenic differentiation of SCAPs by demonstrating the Matrix mineralization.

RESULTS

The highest viability of SCAPs was observed after 24 h in concentration 1 and 10 µg/mL and after 48 h in concentration 1 µg/mL, which were not significantly different from the control group. In both times, the survival of SCAPs decreased with increasing concentration of magnesium oxide nanoparticles (MgONPs). According to the results of Real-time PCR, after 24 and 48 h, the highest differentiation of BSP, DMP1, ALP and DSPP genes was observed in the LED + MgONPs group, followed by MgONPs and then LED, and in all 3 experimental groups, it was significantly higher than control group (P < 0.05). Also, after 24 and 48 h, the density of ARS increased in all groups compared to the control group, and the highest density was observed in the MgONPs + LED and MgONPs groups.

CONCLUSION

This research concluded that exposure to SCAPs, MgONPs, and LED irradiation has a significant effect on enhancing gene expression of odontogenic/osteogenic markers and increasing matrix mineralization.

Magnesium-containing bioceramics stimulate exosomal miR-196a-5p secretion to promote senescent osteogenesis through targeting Hoxa7/MAPK signaling axis

Stem cell senescence is characterized by progressive functional dysfunction and secretory phenotypic changes including decreased proliferation, dysfunction of osteogenic and angiogenic differentiation, increased secretion of the senescence-associated secretory phenotype (SASP), which bring difficulties for bone repair. Rescuing or delaying senescence of aged bone marrow mesenchymal stem cells (O-BMSCs) was considered as effective strategy for bone regeneration in aging microenvironment. Magnesium (Mg) ion released from bioceramics was reported to facilitate bone regeneration via enhancing osteogenesis and alleviating senescence. In this study, Akermanite biocreamics (Akt) containing Mg ion as a model was demonstrated to promote osteogenesis and angiogenesis effects of O-BMSCs by activating the MAPK signaling pathway in vitro. Moreover, the enhanced osteogenesis effects might be attributed to enhanced Mg-containing Akt-mediated exosomal miR-196a-5p cargo targeting Hoxa7 and activation of MAPK signaling pathway. Furthermore, the in vivo study confirmed that 3D-printed porous Mg-containing Akt scaffolds effectively increased bone regeneration in cranial defects of aged rats. The current results indicated that the exosomal-miR-196a-5p/Hoxa7/MAPK signaling axis might be the potential mechanism underlying Akt-mediated osteogenesis. The exosome-meditaed therapy stimulated by the released Mg ion contained in Akt biocreamics or other biomaterials might serve as a candidate strategy for bone repair in aged individuals.

Magnesium-based alloys with adapted interfaces for bone implants and tissue engineering

Magnesium and its alloys are one of the most used materials for bone implants and tissue engineering. They are characterized by numerous advantages such as biodegradability, high biocompatibility and mechanical properties with values close to the human bone. Unfortunately, the implant surface must be adequately tuned, or Mg-based alloys must be alloyed with other chemical elements due to their increased corrosion effect in physiological media. This article reviews the clinical challenges related to bone repair and regeneration, classifying bone defects and presenting some of the most used and modern therapies for bone injuries, such as Ilizarov or Masquelet techniques or stem cell treatments. The implant interface challenges are related to new bone formation and fracture healing, implant degradation and hydrogen release. A detailed analysis of mechanical properties during implant degradation is extensively described based on different literature studies that included in vitro and in vivo tests correlated with material properties' characterization. Mg-based trauma implants such as plates and screws, intramedullary nails, Herbert screws, spine cages, rings for joint treatment and regenerative scaffolds are presented, taking into consideration their manufacturing technology, the implant geometrical dimensions and shape, the type of in vivo or in vitro studies and fracture localization. Modern technologies that modify or adapt the Mg-based implant interfaces are described by presenting the main surface microstructural modifications, physical deposition and chemical conversion coatings. The last part of the article provides some recommendations from a translational perspective, identifies the challenges associated with Mg-based implants and presents some future opportunities. This review outlines the available literature on trauma and regenerative bone implants and describes the main techniques used to control the alloy corrosion rate and the cellular environment of the implant.

Associations of genome-wide structural variations with phenotypic differences in cross-bred Eurasian pigs

BACKGROUND

During approximately 10,000 years of domestication and selection, a large number of structural variations (SVs) have emerged in the genome of pig breeds, profoundly influencing their phenotypes and the ability to adapt to the local environment. SVs (≥ 50 bp) are widely distributed in the genome, mainly in the form of insertion (INS), mobile element insertion (MEI), deletion (DEL), duplication (DUP), inversion (INV), and translocation (TRA). While studies have investigated the SVs in pig genomes, genome-wide association studies (GWAS)-based on SVs have been rarely conducted.

RESULTS

Here, we obtained a high-quality SV map containing 123,151 SVs from 15 Large White and 15 Min pigs through integrating the power of several SV tools, with 53.95% of the SVs being reported for the first time. These high-quality SVs were used to recover the population genetic structure, confirming the accuracy of genotyping. Potential functional SV loci were then identified based on positional effects and breed stratification. Finally, GWAS were performed for 36 traits by genotyping the screened potential causal loci in the F2 population according to their corresponding genomic positions. We identified a large number of loci involved in 8 carcass traits and 6 skeletal traits on chromosome 7, with FKBP5 containing the most significant SV locus for almost all traits. In addition, we found several significant loci in intramuscular fat, abdominal circumference, heart weight, and liver weight, etc. CONCLUSIONS: We constructed a high-quality SV map using high-coverage sequencing data and then analyzed them by performing GWAS for 25 carcass traits, 7 skeletal traits, and 4 meat quality traits to determine that SVs may affect body size between European and Chinese pig breeds.

The Capacity of Magnesium to Induce Osteoclast Differentiation Is Greatly Enhanced by the Presence of Zoledronate

Bisphosphonates (BPs) are successfully used to cure a number of diseases characterized by a metabolic reduction in bone density, such as Osteoporosis, or a neoplastic destruction of bone tissue, such as multiple myeloma and bone metastases. These drugs exert their therapeutic effect by causing a systemic osteoclast depletion that, in turn, is responsible for reduced bone resorption. Unfortunately, in addition to their beneficial activity, BPs can also determine a frightening side effect known as osteonecrosis of the jaw (ONJ). It is generally believed that the inability of osteoclasts to dispose of inflamed/necrotic bone represents the main physiopathological aspect of ONJ. In principle, a therapeutic strategy able to elicit a local re-activation of osteoclast production could counteract ONJ and promote the healing of its lesions. Using an experimental model of Vitamin D3-dependent osteoclastogenesis, we have previously demonstrated that Magnesium is a powerful inducer of osteoclast differentiation. Here we show that, surprisingly, this effect is greatly enhanced by the presence of Zoledronate, chosen for our study because it is the most effective and dangerous of the BPs. This finding allows us to hypothesize that Magnesium might play an important role in the topical therapy of ONJ.

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.

Alkaline earth metals for osteogenic scaffolds: From mechanisms to applications

Regeneration of bone defects is a significant challenge today. As alternative approaches to the autologous bone, scaffold materials have remarkable features in treating bone defects; however, the various properties of current scaffold materials still fall short of expectations. Due to the osteogenic capability of alkaline earth metals, their application in scaffold materials has become an effective approach to improving their properties. Furthermore, numerous studies have shown that combining alkaline earth metals leads to better osteogenic properties than applying them alone. In this review, the physicochemical and physiological characteristics of alkaline earth metals are introduced, mainly focusing on their mechanisms and applications in osteogenesis, especially magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Furthermore, this review highlights the possible cross-talk between pathways when alkaline earth metals are combined. Finally, some of the current drawbacks of scaffold materials are enumerated, such as the high corrosion rate of Mg scaffolds and defects in the mechanical properties of Ca scaffolds. Moreover, a brief perspective is also provided regarding future directions in this field. It is worth exploring that whether the levels of alkaline earth metals in newly regenerated bone differs from those in normal bone. The ideal ratio of each element in the bone tissue engineering scaffolds or the optimal concentration of each elemental ion in the created osteogenic environment still needs further exploration. The review not only summarizes the research developments in osteogenesis but also offers a direction for developing new scaffold materials.

Association between Serum Magnesium and Fractures: A Systematic Review and Meta-Analysis of Observational Studies

Magnesium, an essential cation for numerous cellular processes, is a major component of bone. However, its relationship with the risk of fractures is still uncertain. The present systematic review and meta-analysis aim to investigate the impact of serum Mg on the risk of incident fractures. A systematic search was conducted using several databases including PubMed/Medline and Scopus from inception to 24 May 2022, including observational studies investigating serum Mg and the incidence of fractures considered as outcomes. Abstract and full-text screenings, data extractions, and risk of bias assessments were conducted by two investigators independently. Any inconsistencies were resolved by consensus with a third author. The Newcastle–Ottawa Scale was used to assess the study quality/risk of bias. Among 1332 records initially screened, 16 were retrieved as full-texts; of them, four papers were included in the systematic review with a total of 119,755 participants. We found that lower serum Mg concentrations were associated with a significantly higher risk of incident fractures (RR = 1.579; 95%CI: 1.216–2.051; p = 0.001; I2 = 46.9%). Our systematic review with meta-analysis suggests a strong association of serum Mg concentrations with incident fractures. Further research is needed to confirm our results among other populations and to assess whether serum Mg is potentially relevant in the prevention of fractures, which continue to increase and represent a significant health burden due to the associated disability.

Comparative Osteogenesis and Degradation Behavior of Magnesium Implant in Epiphysis and Diaphysis of the Long Bone in the Rat Model

Magnesium (Mg), as a biodegradable material, is a promising candidate for orthopedic surgery. Long-bone fractures usually occur in cancellous-bone-rich epiphysis at each end or the cortical-rich diaphysis in the center, with different bone healing processes. Little is known about the differences in results between the two regions when applying Mg implants. Therefore, this study aimed to compare the biodegradation and osteogenesis of Mg implants in a rat model's epiphysis and diaphysis of the long bone. Twelve male Sprague Dawley rats underwent Mg rod implantation in the distal femoral epiphyses and tibial diaphyses. Every three weeks for up to twelve weeks, degradation behavior, gas evolution, and new bone formation were measured by micro CT. Histomorphology was analyzed by Hematoxylin and Eosin, Villanueva bone staining, and TRAP staining for osteoclastogenesis evaluations. Micro-CT analysis showed statistically significant higher new bone formation in the epiphysis group than in the diaphysis group, which correlated with a lower gas volume. Histological analysis showed higher osseointegration of Mg implants in the epiphyseal region than in the diaphyseal region. The magnesium implant's osteoclastogenesis-inhibiting properties were shown in the surrounding areas in both the cortical bone of the diaphysis and the cancellous bone of the epiphysis. Our findings show the differences in the magnesium implant's osteogenesis and biodegradation in the epiphysis and the diaphysis. These dissimilarities indicate a better response of the epiphyseal region to the Mg implants, a promising biomaterial for orthopedic surgery applications.

Developing a novel calcium magnesium silicate/graphene oxide incorporated silk fibroin porous scaffold with enhanced osteogenesis, angiogenesis and inhibited osteoclastogenesis

Recently, biofunctional ions (Mg2+, Si4+, etc.) and graphene derivatives are proved to be promising in stimulating bone formation. In this study, a novel inorganic/organic composite porous scaffold based on silk fibroin (SF), graphene oxide (GO), and calcium magnesium silicate (CMS) was developed for bone repair. The porous scaffolds obtained by lyophilization showed a little difference in pore structure while GO and CMS displayed a good interaction with SF matrix. The addition of CMS with good mineralization potential and sustainedly release ability of biofunctional ions (Ca2+, Mg2+ and Si4+) increased the strength of SF scaffolds a little and facilitated the osteogenic differentiation of bone mesenchymal stem cells (BMSCs) by upregulating bone formation-related genes (ALP, COL1, OC and Runx2). The further incorporation of GO in SF scaffolds enhanced the compressive strength and water retention, and also remarkably promoted the osteogenic differentiation of BMSCs. Besides, the angiogenesis of human umbilical vein endothelial cells was significantly promoted by CMS/GO/SF scaffold extract through the upregulation of angiogenesis genes (eNOs and bFGF). Moreover, the osteoclastic formation ability of RAW264.7 cells was suppressed by the released ions from CMS/GO/SF scaffold through the down-regulation of CAK, MMP9 and TRAP. The promoted osteogenesis, angiogenesis and inhibited osteoclastogenesis functions of CMS/GO/SF composite scaffold may enable it as a novel therapy for bone repair and regeneration.

Long-term use of proton pump inhibitors adversely affects minerals and vitamin metabolism, bone turnover, bone mass, and bone strength

Notwithstanding, proton pump inhibitors (PPIs) are one of the most excellent options for different anti-secretory therapy in terms of improved symptomatic outcomes, numerous epidemiological and cohort studies provide evidence of an association between long-term proton PPIs use and increased fracture risk among users. The present attempt aimed to summarize the effect of long-term use of PPIs on musculoskeletal systems by considering the recent claims of different research groups to understand the risk of osteopenia and osteoporosis and to determine the risk factors associated with these complications. We extracted data from various systematic reviews and meta-analyses, cross-sectional studies, prospective studies, case-control studies, cohort studies, and in-vivo and in-vitro studies to observe the consequence of long-term PPIs uses over the patient's bone health. Recent findings suggested that long-term use of PPIs plays an introductory and cabalistic role in the development of osteoporosis mostly hip fractures by disturbing numerous biological pathways and thus able to set up a link between over-prescription of PPIs and bone loss. Frequent administration of PPIs is associated with a significantly worse outcome to bone mineral density (BMD) profile and produce a negative impression on bone health. Since, there are limited data to determine the association of PPIs use and change in BMD, recommending further studies to find out this dissertation.

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.

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.

Resorbable Mg2+-Containing Phosphates for Bone Tissue Repair

Materials based on Mg2+-containing phosphates are gaining great relevance in the field of bone tissue repair via regenerative medicine methods. Magnesium ions, together with condensed phosphate ions, play substantial roles in the process of bone remodeling, affecting the early stage of bone regeneration through active participation in the process of osteosynthesis. In this paper we provide a comprehensive overview of the usage of biomaterials based on magnesium phosphate and magnesium calcium phosphate in bone reconstruction. We consider the role of magnesium ions in angiogenesis, which is an important process associated with osteogenesis. Finally, we summarize the biological properties of calcium magnesium phosphates for regeneration of bone.

Impact of serum magnesium and bone mineral density on systemic fractures in chronic hemodialysis patients

Introduction

Bone mineral density (BMD) measured with dual-energy X-ray absorptiometry (DXA) can be used to predict fractures, but its clinical utility has not been fully established in chronic kidney disease (CKD) patients. Magnesium is an essential trace element. Although magnesium is associated with the risk of fractures in non-CKD populations, the relationship is unknown in CKD patients.

Methods

BMD and serum magnesium levels were measured in 358 stable outpatients undergoing maintenance hemodialysis therapy. The primary outcome was fragility fracture. Patients were divided into groups according to the median level of magnesium and the normal threshold value of lumbar spine BMD.

Results

During the median follow-up period of 36 months, 36 (10.0%) fractures occurred. The cumulative incidence rates of fractures were 17.6% and 5.2% [adjusted hazard ratio (aHR) 2.31, 95% confidence interval (CI) 1.03–5.17, P = 0.030] in the lower (<2.6 mg/dL) and higher (≥2.6 mg/dL) magnesium (Mg) groups, respectively, and 21.2% and 7.3% (aHR 2.59, 95% CI 1.09–6.16, P = 0.027) in the low- and high-BMD groups, respectively. The lower-Mg and low-BMD group had a 9.21-fold higher risk of fractures (95% CI; 2.35–47.00; P = 0.0010) than the higher-Mg and high-BMD group. Furthermore, adding both magnesium levels and lumbar spine BMD levels to the established risk factors significantly improved the prediction of fractures (C-index: 0.784 to 0.830, p = 0.041).

Discussion/Conclusions

The combination of serum magnesium and lumbar spine BMD can be used for fracture risk stratification and synergistically improves the prediction of fractures in CKD patients.

Characterization of magnesium doped sol-gel biomaterial for bone tissue regeneration: The effect of Mg ion in protein adsorption

Magnesium is the fourth most abundant element in the human body with a wide battery of functions in the maintenance of normal cell homeostasis. In the bone, this element incorporates in the hydroxyapatite structure and it takes part in mineral metabolism and regulates osteoclast functions. In this study, sol-gel materials with increasing concentrations of MgCl₂ (0.5, 1, and 1.5%) were synthesized and applied onto Ti surfaces as coatings. The materials were first physicochemically characterized. In vitro responses were examined using the MC3T3-E1 osteoblastic cells and RAW264.7 macrophages. Human serum protein adsorption was evaluated employing nLC-MS/MS. The incorporation of Mg did not affect the crosslinking of the sol-gel network, and a controlled release of Mg was observed; it was not cytotoxic at any of the tested concentrations. The cytoskeleton arrangement of MC3T3-E1 cells cultured on the Mg-doped materials changed in comparison with controls; the cells became more elongated, with protruded lamellipodia and increased cell surface. The expression of integrins (ITGA5 and ITGB1) was boosted by Mg-coatings. The ALP activity and expression of TGF-β, OSX and RUNX2 genes were also increased. In RAW264.7 cells, TNF-α secretion was reduced, while TGF-β and IL-4 expression rose. These changes correlated with the altered protein adsorption patterns. The Mg-doped coatings showed increased adsorption of anti-inflammatory (CLUS, IC1, CFAH, and VTNC), cell adhesion (DSG1, FILA2, and DESP) and tissue regeneration (VTNC and CYTA) proteins. This integrated approach to biomaterial characterization revealed the potential of Mg in bone tissue regeneration.

Synergistic effects of magnesium ions and simvastatin on attenuation of high-fat diet-induced bone loss

Introduction

Magnesium (Mg) has a prophylactic potential against the onset of hyperlipidemia. Similar to statin, Mg is recommended as lipid-lowering medication for hypercholesterolemia and concomitantly exhibits an association with increased bone mass. The combination of statin with Mg ions (Mg²⁺) may be able to alleviate the high-fat diet (HFD)-induced bone loss and reduce the side-effects of statin. This study aimed to explore the feasibility of combined Mg²⁺ with simvastatin (SIM) for treating HFD-induced bone loss in mice and the involving mechanisms.

Materials and methods

C57BL/6 male mice were fed with a HFD or a normal-fat diet (NFD). Mice were intraperitoneally injected SIM and/or orally received water with additional Mg²⁺ until sacrificed. Enzyme-linked immunosorbent assay was performed to measure cytokines and cholesterol in serum and liver lysates. Bone mineral density (BMD) and microarchitecture were assessed by micro-computed tomography (μCT) in different groups. The adipogenesis in palmitate pre-treated HepG2 cells was performed under various treatments.

Results

μCT analysis showed that the trabecular bone mass was significantly lower in the HFD-fed group than that in NFD-fed group since week 8. The cortical thickness in HFD-fed group had a significant decrease at week 24, as compared with NFD-fed group. The combination of Mg²⁺ and SIM significantly attenuated the trabecular bone loss in HFD-fed mice via arresting the osteoclast formation and bone resorption. Besides, such combination also reduced the hepatocytic synthesis of cholesterol and inhibited matrix metallopeptidase 13 (Mmp13) mRNA expression in pre-osteoclasts.

Conclusions

The combination of Mg²⁺ and SIM shows a synergistic effect on attenuating the HFD-induced bone loss. Our current formulation may be a cost-effective alternative treatment to be indicated for obesity-related bone loss.

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High-fat diet-fed mouse has a susceptibility to lower trabecular bone mass as compared with that of normal-fat diet-fed mouse.

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The combination of Mg²⁺ and simvastatin attenuates the trabecular bone loss in high-fat diet-fed mice.

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The combination of Mg²⁺ and simvastatin reduces the hepatocytic synthesis of cholesterol.

Proton Pump Inhibitors and Fractures in Adults: A Critical Appraisal and Review of the Literature

Despite the large number of patients worldwide being on proton pump inhibitors (PPIs) for acid-related gastrointestinal disorders, uncertainty remains over their long-term safety. Particularly, the potential side effects of these drugs on bone health have been evaluated in the last years. The purpose of our narrative review is to gather and discuss results of clinical studies focusing on the interactions between PPIs and fracture risk. Data generated mainly from nested case-control studies and meta-analysis suggest that long-term/high-dose PPIs users are characterized by an increased risk of fragility fractures, mainly hip fractures. However, in these studies, the PPIs-induced bone impairment is often not adjusted for different confounding variables that could potentially affect bone health, and exposure to PPIs was reported using medical prescriptions without adherence evaluation. The mechanisms of the PPI-related bone damage are still unclear, but impaired micronutrients absorption, hypergastrinemia, and increased secretion of histamine may play a role. Clinicians should pay attention when prescribing PPIs to subjects with a preexistent high risk of fractures and consider antiosteoporotic drugs to manage this additive effect on the bone. However, further studies are needed to clarify PPIs action on the bone.

The Association Between the Concentration of Serum Magnesium and Postmenopausal Osteoporosis

Background: Osteoporosis is the most common and widespread chronic skeletal metabolic disease in the world and can lead to catastrophic fractures. Therefore, it is important to look for factors that can be modified or controlled to prevent osteoporosis. Although serum Mg is believed to be associated with osteoporosis in many individuals, there are conflicting reports on the association between serum Mg and osteoporosis. Therefore, this meta-analyses aimed to explore the association between the concentration of serum Mg and osteoporosis as well as that between the concentration of serum Mg and osteopenia.

Methods: Articles were searched in PubMed. We also reviewed the reference lists of the relevant publications and reviews as of December 2019. Finally, 11 eligible studies involving 2,776 postmenopausal women were selected. We performed subgroup analysis, and publication bias was assessed.

Results: According to the forest plot analysis, postmenopausal women with osteoporosis had a lower concentration of serum Mg than normal controls [standardized mean difference (SMD) = −0.56, 95% confidence interval (CI) = −1.02 to −0.09]. However, this result was not applicable to those with osteopenia (SMD = −0.30, 95% CI = −0.69 to 0.09). The subgroup analysis by geographical location found a similar pattern in European postmenopausal women with osteoporosis (SMD = −0.73, 95% CI = −1.322 to −0.143), but not in Asian (SMD = −0.007, 95% CI = −0.381 to 0.394). The subgroup analysis by site of bone mineral density (BMD) showed the serum Mg concentration of postmenopausal women with osteoporosis (BMD of femur) was lower than in healthy controls (SMD = −0.44, 95% CI = −0.77 to −0.12), and BMD of the spine group had the same conclusion (SMD = −0.78, 95% CI = −1.36 to −0.19). Besides, the serum Mg concentration of postmenopausal women with osteoporosis was lower than that of the normal bone mass group in the studies those included more than 50 postmenopausal women with osteoporosis (SMD = −0.57, 95% CI = −1.04 to −0.11). We also found postmenopausal women under the age of 60 with osteoporosis had a lower concentration of serum Mg than the healthy controls (SMD = −0.61, 95% CI = −1.09 to −0.13).

Conclusion: Postmenopausal women with osteoporosis have a lower concentration of serum Mg. However, the association between the concentration of serum Mg and osteopenia needs further confirmation.

Use of proton pump inhibitors in dialysis patients: a double-edged sword?

Large cohort-based studies have shown that proton pump inhibitors (PPIs) are linked to rare but multiple and varied secondary events when used in the general population. Although clinicians accept the negative effects of PPIs on renal function, there is a lack of available data regarding the potential consequences of their use by dialysis patients in whom the risk of gastrointestinal bleeding is quite high. This review aims to highlight the risks and benefits of PPIs use in dialysis patients. To summarize, the benefit on the reduction of high digestive bleeding seems certain, but without any beneficial impact on overall survival. The impact on quality of life seems to be significant. The data on the occurrence of peritonitis during PPIs treatment are very contradictory. There is evidence regarding the occurrence of hypomagnesaemia in haemodialysis patients with PPIs; which may lead to increase bone fragility. New data show an increased cardiovascular risk and even a risk of death linked to the use of PPIs on dialysis. Several mechanisms of IPP toxicity are advanced to explain these findings.

MicroRNA-16, via FGF2 Regulation of the ERK/MAPK Pathway, Is Involved in the Magnesium-Promoted Osteogenic Differentiation of Mesenchymal Stem Cells

microRNAs (miRNAs) participate in the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). However, few reports have discussed the effect of miRNAs on the magnesium chloride (MgCl₂)-induced promotion of osteogenic differentiation of BMSCs, a process involved in the healing of bone tissue. As determined in the present investigation, MgCl₂ decreased miR-16 levels; increased levels of fibroblast growth factor 2 (FGF2), p-p38, and p-ERK; and promoted the osteogenic differentiation of BMSCs. Enhancement of miR-16 levels by an miR-16 mimic blocked these MgCl₂-induced changes. Moreover, luciferase reporter assays confirmed that miR-16 binds to the 3'UTR region of FGF2 mRNA. Down-regulation of FGF2 blocked the MgCl₂-induced increases of p-p38 and p-ERK and the promotion of the osteogenic differentiation of BMSCs. Furthermore, over-expression of miR-16 attenuated the MgCl₂-induced overproduction of p-p38 and p-ERK1/2 and the high levels of osteogenic differentiation, effects that were reversed by elevated expression of FGF2. In summary, the present findings provide a mechanism by which miR-16 regulates MgCl₂-induced promotion of osteogenic differentiation by targeting FGF2-mediated activation of the ERK/MAPK pathway.

Biodegradable Magnesium-Based Implants in Orthopedics-A General Review and Perspectives

Biodegradable Mg-based metals may be promising orthopedic implants for treating challenging bone diseases, attributed to their desirable mechanical and osteopromotive properties. This Review summarizes the current status and future research trends for Mg-based orthopedic implants. First, the properties between Mg-based implants and traditional orthopedic implants are compared on the following aspects: in vitro and in vivo degradation mechanisms of Mg-based implants, peri-implant bone responses, the fate of the degradation products, and the cellular and molecular mechanisms underlying the beneficial effects of Mg ions on osteogenesis. Then, the preclinical studies conducted at the low weight bearing sites of animals are introduced. The innovative strategies (for example, via designing Mg-containing hybrid systems) are discussed to address the limitations of Mg-based metals prior to their clinical applications at weight-bearing sites. Finally, the available clinical studies are summarized and the challenges and perspectives of Mg-based orthopedic implants are discussed. Taken together, the progress made on the development of Mg-based implants in basic, translational, and clinical research has laid down a foundation for developing a new era in the treatment of challenging and prevalent bone diseases.

Magnesium: An old player revisited in the context of CKD-MBD

Chronic kidney disease (CKD) is associated with a wide number of abnormalities in mineral metabolism. Often, these alterations are the leading players in the development of comorbidities associated with CKD, which are risk factors of mortality. In this context, mineral and bone disorder associated with CKD (CKD-MBD) are highlighted, connecting bone, renal, and cardiovascular disorders. Many studies have been led to propose strategies to avoid, reduce, or slow down CKD-MBD progression using different compositions of metallic elements-based P binders such as aluminum, magnesium, or calcium. Magnesium, the aim of this review, has been used by nephrologists to treat CKD-MBD with a variable acceptation due mainly to different results on bone homeostasis. Nowadays, we have new evidence about the efficacy of magnesium supplementation on vascular calcification, renal function, and bone disorders, suggesting potential beneficial effects of Magnesium in the management of CKD-MBD.

Biomarkers of Osteoporosis: An Update

Background:

Osteoporosis, characterized by compromised bone quality and strength is associated with bone fragility and fracture risk. Biomarkers are crucial for the diagnosis or prognosis of a disease as well as elucidating the mechanism of drug action and improve decision making.

Objective:

An exhaustive description of traditional markers including bone mineral density, vitamin D, alkaline phosphatase, along with potential markers such as microarchitectural determination, trabecular bone score, osteocalcin, etc. is provided in the current piece of work. This review provides insight into novel pathways such as the Wnt signaling pathway, neuro-osseous control, adipogenic hormonal imbalance, gut-bone axis, genetic markers and the role of inflammation that has been recently implicated in osteoporosis.

Methods:

We extensively reviewed articles from the following databases: PubMed, Medline and Science direct. The primary search was conducted using a combination of the following keywords: osteoporosis, bone, biomarkers, bone turnover markers, diagnosis, density, architecture, genetics, inflammation.

Conclusion:

Early diagnosis and intervention delay the development of disease and improve treatment outcome. Therefore, probing for novel biomarkers that are able to recognize people at high risk for developing osteoporosis is an effective way to improve the quality of life of patients and to understand the pathomechanism of the disease in a better way.

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.

In vivo stability evaluation of Mg substituted low crystallinity ß-tricalcium phosphate granules fabricated through dissolution-precipitation reaction for bone regeneration

Although β-tricalcium phosphate (β-TCP) is widely used in clinical applications as a bone substitute owing to its positive tissue response and its ability to be replaced by new bone through a bone-remodeling process, it has the limitation of rapid resorption in vivo, which might become a reason for tissue atrophy and high crystallinity, which decrease biocompatibility. A reduction in the crystallinity might increase the biocompatibility of the bone substitute. To overcome the drawbacks of β-TCP, decrease in crystallinity and solubility, both are required. Therefore, in this study, the feasibility of fabricating Mg substituted low crystalline β-TCP (Mg-LC-β-TCP) granules formed in aqueous solution was evaluated in vivo focusing long-term adsorption and bone formation in bone defects formed in the rabbit femur using sintered β-TCP granules as a control. With Mg-LC-β-TCP, the resorption of the substitute was suppressed, and no tissue atrophy was observed even at 24 weeks post-implantation, whereas a few granules with surrounding tissue atrophy were observed at 12 weeks post-implantation. Tartrate-resistant acid phosphatase-staining indicated that the density of osteoclasts type cells with Mg-LC-β-TCP was significantly lower than that with β-TCP, and also the numbers of osteoblasts type cells with Mg-LC-β-TCP were significantly higher than that with β-TCP. It is suggested that Mg substitution to form low crystallinity β-TCP is a valuable way to overcome the limitations of β-TCP as a bone substitute.

The effect of osteoblasts on the surface oxidation processes of biodegradable Mg and Mg-Ag alloys studied by synchrotron IR microspectroscopy

High-resolution analytical methods, including synchrotron infrared microspectroscopy combined with wavelength-dispersive X-ray emission spectroscopy were applied to study the structure and chemical composition of the oxidized layer of pure and Ag-alloyed Mg exposed to cell culture media without and with osteoblasts. Comparative analysis has been done on pure Mg immersed in two different cell culture media: Dulbecco's Modified Eagle's Medium (DMEM) and Roswell Park Memorial Institute medium (RPMI), whereas Mg-xAg binary alloys (x = 2, 4, 6, 8 wt%) were studied after immersion in DMEM. It is shown that the physicochemical formation of degradation products as well as the activity of the biological component is influenced by the addition of silver. It could be demonstrated that the presence of Ag in the Mg alloy enhances the chemical reaction between Mg and C to form amorphous and/or crystalline MgCO₃ on account of CaCO₃. As a consequence, the further available P and Ca react easily to form Mg-poor amorphous calcium phosphate phases. Osteoblasts actively adjusted these phases towards hydroxyapatite-like phases.

Magnesium and Risk of Hip Fracture among Patients Undergoing Hemodialysis

Magnesium is an essential mineral for bone metabolism. However, little is known about the relationship between magnesium and the risk of fractures. In this cohort study, we elucidated the association between serum magnesium level and the risk of incident hip fracture among patients undergoing hemodialysis. We identified 113,683 patients undergoing hemodialysis with no history of hip fracture from a nation-wide database of patients undergoing dialysis in Japan. During a 2-year follow-up, a total of 2305 (2%) new hip fractures occurred. The crude incidence rate was significantly higher among patients in the lower quartiles of serum magnesium levels (2.63%, 2.08%, 1.76%, and 1.49% in Q1-Q4, respectively; P<0.001 for trend). The range of serum magnesium levels (in milligrams per deciliter) in each quartile was as follows: Q1, <2.3; Q2, 2.4-2.6; Q3, 2.7-2.8, and Q4, >2.9. After adjustment for demographic and clinical factors, patients in Q1 had a 1.23-fold higher risk for hip fracture than those in Q4 (95% confidence interval, 1.06 to 1.44; P<0.01). Similarly, an inverse probability weighting analysis showed an increased risk of hip fracture among patients in the lower magnesium quartiles. We did not observe significant effect modifications in subgroup analyses. The population-attributable fraction of serum magnesium level for incident hip fractures was 13.7% (95% confidence interval, 3.7% to 22.7%), which was much higher than that of serum calcium, serum phosphate, and parathyroid hormone levels. Thus, mild hypermagnesemia is associated with a lower risk of hip fracture among patients undergoing hemodialysis.

Role of lysosomal channel protein TPC2 in osteoclast differentiation and bone remodeling under normal and low-magnesium conditions

The bone is the main storage site for Ca²⁺ and Mg²⁺ ions in the mammalian body. Although investigations into Ca²⁺ signaling have progressed rapidly and led to better understanding of bone biology, the Mg²⁺ signaling pathway and associated molecules remain to be elucidated. Here, we investigated the role of a potential Mg²⁺ signaling-related lysosomal molecule, two-pore channel subtype 2 (TPC2), in osteoclast differentiation and bone remodeling. Previously, we found that under normal Mg²⁺ conditions, TPC2 promotes osteoclastogenesis. We observed that under low-Mg²⁺ conditions, TPC2 inhibited, rather than promoted, the osteoclast differentiation and that the phosphatidylinositol 3,5-bisphosphate (PI(3,5)P₂) signaling pathway played a role in the TPC2 activation under low-Mg²⁺ conditions. Furthermore, PI(3,5)P₂ depolarized the membrane potential by increasing the intracellular Na⁺ levels. To investigate how membrane depolarization affects osteoclast differentiation, we generated a light-sensitive cell line and developed a system for the light-stimulated depolarization of the membrane potential. The light-induced depolarization inhibited the osteoclast differentiation. We then tested the effect of myo-inositol supplementation, which increased the PI(3,5)P₂ levels in mice fed a low-Mg²⁺ diet. The myo-inositol supplementation rescued the low-Mg²⁺ diet-induced trabecular bone loss, which was accompanied by the inhibition of osteoclastogenesis. These results indicate that low-Mg²⁺-induced osteoclastogenesis involves changes in the role of TPC2, which are mediated through the PI(3,5)P₂ pathway. Our findings also suggest that myo-inositol consumption might provide beneficial effects in Mg²⁺ deficiency-induced skeletal diseases.

Akermanite used as an alkaline biodegradable implants for the treatment of osteoporotic bone defect

In osteoporosis scenario, tissue response to implants is greatly impaired by the deteriorated bone regeneration microenvironment. In the present study, a Mg-containing akermanite (Ak) ceramic was employed for the treatment of osteoporotic bone defect, based on the hypothesis that both beneficial ions (e.g. Mg2+ect.) released by the implants and the weak alkaline microenvironment pH (μe-pH) it created may play distinct roles in recovering the abnormal bone regeneration by stimulating osteoblastic anabolic effects. The performance of Ak, β-tricalcium phosphate (β-TCP) and Hardystone (Har) in healing a 3 mm bone defect on the ovariectomized (OVX) osteoporotic rat model was evaluated. Our results indicated that, there's more new bone formed in Ak group than in β-TCP or Har group at week 9. The initial μe-pHs of Ak were significantly higher than that of the β-TCP and Blank group, and this weak alkaline condition was maintained till at least 9 weeks post-surgery. Increased osteoblastic activity which was indicated by higher osteoid secretion was observed in Ak group at week 4 to week 9. An intermediate layer which was rich in phosphorus minerals and bound directly to the new forming bone was developed on the surface of Ak. In a summary, our study demonstrates that Ak exhibits a superior bone regenerative performance under osteoporosis condition, and might be a promising candidate for the treatment of osteoporotic bone defect and fracture.

Effect of the biodegradation rate controlled by pore structures in magnesium phosphate ceramic scaffolds on bone tissue regeneration in vivo

Similar to calcium phosphates, magnesium phosphate (MgP) ceramics have been shown to be biocompatible and support favorable conditions for bone cells. Micropores below 25μm (MgP25), between 25 and 53μm (MgP53), or no micropores (MgP0) were introduced into MgP scaffolds using different sizes of an NaCl template. The porosities of MgP25 and MgP53 were found to be higher than that of MgP0 because of their micro-sized pores. Both in vitro and in vivo analysis showed that MgP scaffolds with high porosity promoted rapid biodegradation. Implantation of the MgP0, MgP25, and MgP53 scaffolds into rabbit calvarial defects (with 4- and 6-mm diameters) was assessed at two times points (4 and 8weeks), followed by analysis of bone regeneration. The micro-CT and histologic analyses of the 4-mm defect showed that the MgP25 and MgP53 scaffolds were degraded completely at 4weeks with simultaneous bone and marrow-like structure regeneration. For the 6-mm defect, a similar pattern of regeneration was observed. These results indicate that the rate of degradation is associated with bone regeneration. The MgP25 and MgP53 scaffold-implanted bone showed a better lamellar structure and enhanced calcification compared to the MgP0 scaffold because of their porosity and degradation rate. Tartrate-resistant acid phosphatase (TRAP) staining indicated that the newly formed bone was undergoing maturation and remodeling. Overall, these data suggest that the pore architecture of MgP ceramic scaffolds greatly influence bone formation and remodeling activities and thus should be considered in the design of new scaffolds for long-term bone tissue regeneration.

STATEMENT OF SIGNIFICANCE

The pore structural conditions of scaffold, including porosity, pore size, pore morphology, and pore interconnectivity affect cell ingrowth, mechanical properties and biodegradabilities, which are key components of scaffold in bone tissue regeneration. In this study, we designed hierarchical pore structure of the magnesium phosphate (MgP) scaffold by combination of the 3D printing process, self-setting reaction and salt-leaching technique, and first studied the effect of pore structures of bioceramic scaffolds on bone tissue regeneration through both in vitro and in vivo studies (rabbit calvarial model). The MgP scaffolds with higher porosity promoted more rapid biodegradation and enhanced new bone formation and remodeling activities at the same time.

The Degradation Interface of Magnesium Based Alloys in Direct Contact with Human Primary Osteoblast Cells

Magnesium alloys have been identified as a new generation material of orthopaedic implants. In vitro setups mimicking physiological conditions are promising for material / degradation analysis prior to in vivo studies however the direct influence of cell on the degradation mechanism has never been investigated. For the first time, the direct, active, influence of human primary osteoblasts on magnesium-based materials (pure magnesium, Mg-2Ag and Mg-10Gd alloys) is studied for up to 14 days. Several parameters such as composition of the degradation interface (directly beneath the cells) are analysed with a scanning electron microscope equipped with energy dispersive X-ray and focused ion beam. Furthermore, influence of the materials on cell metabolism is examined via different parameters like active mineralisation process. The results are highlighting the influences of the selected alloying element on the initial cells metabolic activity.

Magnesium from bioresorbable implants: Distribution and impact on the nano- and mineral structure of bone

Biocompatibility is a key issue in the development of new implant materials. In this context, a novel class of biodegrading Mg implants exhibits promising properties with regard to inflammatory response and mechanical properties. The interaction between Mg degradation products and the nanoscale structure and mineralization of bone, however, is not yet sufficiently understood. Investigations by synchrotron microbeam x-ray fluorescence (μXRF), small angle x-ray scattering (μSAXS) and x-ray diffraction (μXRD) have shown the impact of degradation speed on the sites of Mg accumulation in the bone, which are around blood vessels, lacunae and the bone marrow. Only at the highest degradation rates was Mg found at the implant-bone interface. The Mg inclusion into the bone matrix appeared to be non-permanent as the Mg-level decreased after completed implant degradation. μSAXS and μXRD showed that Mg influences the hydroxyl apatite (HAP) crystallite structure, because markedly shorter and thinner HAP crystallites were found in zones of high Mg concentration. These zones also exhibited a contraction of the HAP lattice and lower crystalline order.

Effects of extracellular magnesium on the differentiation and function of human osteoclasts

Magnesium-based implants have been shown to influence the surrounding bone structure. In an attempt to partially reveal the cellular mechanisms involved in the remodelling of magnesium-based implants, the influence of increased extracellular magnesium content on human osteoclasts was studied. Peripheral blood mononuclear cells were driven towards an osteoclastogenesis pathway via stimulation with receptor activator of nuclear factor kappa-B ligand and macrophage colony-stimulating factor for 28 days. Concomitantly, the cultures were exposed to variable magnesium concentrations (from either magnesium chloride or magnesium extracts). Osteoclast proliferation and differentiation were evaluated based on cell metabolic activity, total protein content, tartrate-resistant acid phosphatase activity, cathepsin K and calcitonin receptor immunocytochemistry, and cellular ability to form resorption pits. While magnesium chloride first enhanced and then opposed cell proliferation and differentiation in a concentration-dependent manner (peaking between 10 and 15mM magnesium chloride), magnesium extracts (with lower magnesium contents) appeared to decrease cell metabolic activity (≈50% decrease at day 28) while increasing osteoclast activity at a lower concentration (twofold higher). Together, the results indicated that (i) variations in the in vitro extracellular magnesium concentration affect osteoclast metabolism and (ii) magnesium extracts should be used preferentially in vitro to more closely mimic the in vivo environment.

Association between serum level of magnesium and postmenopausal osteoporosis: a meta-analysis

There are conflicting reports as to the association between serum level of magnesium (Mg) and postmenopausal osteoporosis (OP). The purpose of the present study is to clarify the association between serum level of Mg and postmenopausal OP using a meta-analysis approach. We searched articles indexed in Pubmed and the Chinese Journal Full-text Database (CJFD) published as of October 2013 that met our predefined criteria. Seven eligible studies involving 1,349 postmenopausal women from 12 case-control study arms were identified. Overall, pooled analysis indicated that postmenopausal osteoporotic women had a lower serum level of Mg than the healthy controls (standardized mean difference [SMD]=-0.55, 95 % confidence interval [CI]=-0.83 to -0.26). Further subgroup analysis found a similar pattern in Turkey (SMD=-0.66, 95% CI=-0.99 to -0.32) and Belgium (SMD=-0.98, 95% CI=-1.91 to -0.05), but not in China (SMD=0.02, 95% CI=-0.21 to 0.26). And the difference of serum level of Mg between postmenopausal osteoporotic women and healthy controls below the age of 60 years (SMD=-0.61, 95% CI=-1.09 to -0.13) was similar to that among the population over 60 years (SMD=-0.49, 95% CI=-0.80 to -0.18).In conclusion, this meta-analysis suggests that the low serum level of Mg seems to be a risk factor for OP among the postmenopausal women. However, the subgroup analysis found that there was contradiction regarding races and geography, like China and Turkey. Thus, this finding needs further confirmation by trans-regional multicenter study to obtain better understanding of causal relationships between serum Mg and postmenopausal OP.

Magnesium-containing nanostructured hybrid scaffolds for enhanced dentin regeneration

Dental caries is one of the most prevalent chronic diseases in the United States, affecting 92% of adults aged 20-64 years. Scaffold-based tissue engineering represents a promising strategy to replace damaged dental structures and restore their biological functions. Current single-component scaffolding materials used for dental tissue regeneration, however, cannot provide the proper microenvironment for dental stem/progenitor cell adhesion, proliferation, and differentiation; new biomimetic hybrid scaffolds are needed to promote better dental tissue formation. In this work, we developed a biomimetic approach to prepare three-dimensional (3D) nanofibrous gelatin/magnesium phosphate (NF-gelatin/MgP) hybrid scaffolds. These scaffolds not only mimic the nanostructured architecture and the chemical composition of natural dentin matrices but also constantly present favorable chemical signals (Mg ions) to dental pulp stem cells (DPSCs), thus providing a desirable microenvironment to facilitate DPSC proliferation, differentiation, and biomineralization. Synthesized hybrid NF-gelatin/MgP possesses natural extracellular matrix (ECM)-like architecture, high porosity, high pore interconnectivity, well-defined pore size, and controlled Mg ion release from the scaffold. Adding MgP into NF-gelatin also increased the mechanical strength of the hybrid scaffold. The sustained release of Mg ions from the NF-gelatin/MgP (MgP=10% wt/wt) scaffold significantly enhanced the proliferation, differentiation, and biomineralization of human DPSCs in vitro. The alkaline phosphatase (ALP) activity and the gene expressions for odontogenic differentiation (collagen I [Col I], ALP, osteocalcin [OCN], dentin sialophosphoprotein [DSPP], and dentin matrix protein 1 [DMP1]) were all significantly higher (p<0.05) in the NF-gelatin/MgP group than in the NF-gelatin group. Those results were further confirmed by hematoxylin and eosin (H&E) and von Kossa staining, as shown by greater ECM secretion and mineral deposition in the hybrid scaffold. Consistent with the in vitro study, the DPSCs/NF-gelatin/MgP constructs produced greater ECM deposition, hard tissue formation, and expression of marker proteins (DSPP, DMP1, Col I) for odontogenic differentiation than did the DPSCs/NF-gelatin after 5 weeks of ectopic implantation in rude mice. The controlled release of metallic ions from biomimetic nanostructured hybrid scaffolds, therefore, is a promising approach to enhancing the biological capability of the scaffolds for dental tissue regeneration.

Magnesium and osteoporosis: current state of knowledge and future research directions

A tight control of magnesium homeostasis seems to be crucial for bone health. On the basis of experimental and epidemiological studies, both low and high magnesium have harmful effects on the bones. Magnesium deficiency contributes to osteoporosis directly by acting on crystal formation and on bone cells and indirectly by impacting on the secretion and the activity of parathyroid hormone and by promoting low grade inflammation. Less is known about the mechanisms responsible for the mineralization defects observed when magnesium is elevated. Overall, controlling and maintaining magnesium homeostasis represents a helpful intervention to maintain bone integrity.