Effects of fluctuant magnesium concentration on phenotype of the primary chondrocytes

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

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

Sol-gel synthesis of magnesium oxide nanoparticles and their evaluation as a therapeutic agent for the treatment of osteoarthritis

Aim: We synthesized MgO NPs via sol-gel reaction and investigated them as carriers to deliver Mg2+ to the affected joint for osteoarthritis (OA).Materials & methods: The physicochemical properties of samples were characterized by transmission electron microscope (TEM), dynamic light scattering (DLS) and x-ray diffraction (XRD). The release of Mg2+ was monitored by ICP-MS. The potential cytotoxicity was evaluated using MTT assay. The efficacy and biosafety were evaluated in a rabbit OA model.Results: MgO NPs can prolong the Mg2+ release time from 0.5 h to 12 h. No significant cytotoxicity was observed when concentrations below 250 μg/ml. Intra-articular samples could effectively alleviate the degeneration and destruction of the cartilage.Conclusion: this study demonstrates the potential of MgO NPs as a safe and effective treatment of OA. Simultaneously, the size of the particles may play a significant role in influencing the therapeutic outcome.

Effect of unsoluble corrosion products of WE43 alloys in vitro on macrophages

Magnesium alloys have been used to manufacture biodegradable implants, bone graft substitutes, and cardiovascular stents. WE43 was the most widely used magnesium alloy. The degradation process begins when the magnesium alloy stent is implanted in the body and comes into contact with body fluid. The degradation products include hydrogen, Mg2+ , local alkaline environment, and unsoluble products. A large number of studies focused on Mg2+ and pH in vitro, and in vivo of magnesium alloys, but few studies on unsoluble corrosion products (UCPs). In this study, UCPs of WE43 alloy were prepared by immersion in vitro, and their effects on macrophages were investigated. The results showed that the unsoluble corrosion products were Mg24Y5, Mg12YNd, and MgCO3 ·3H2 O, which were dose-dependent on the apoptosis and necrosis of macrophages. After phagocytosis of UCPs, macrophages mainly metabolize in lysosome, and autophagy also participates in the metabolism of UCPs. It also decreases mitochondrial membrane potential and increases lysosomes, endoplasmic reticulum stress, and P2X7 receptor activation. These will increase reactive oxygen species (ROS) in cells, activating NLRP3 inflammatory corpuscles, activating the downstream pro-IL18 and pro-IL1β, and converting it to IL-18, and IL-1β. However, its pro-inflammatory effect is far lower than that of the classical Lipopolysaccharide (LPS) pro-inflammatory pathway. This work has increased our understanding of magnesium alloy metabolism and provides new ideas for the clinical application of magnesium alloys.

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.

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.

The responses of human gingival fibroblasts to magnesium-doped titanium

The titanium (Ti) implant is widely used in implant dentistry; yet peri-implantitis has always been one of the most common and serious complications. Here, we demonstrated that magnesium-doping would be an effective way of enhancing the integration between implant surfaces and gingival tissues, which is critical to peri-implant health. The magnesium (2.76-6.35 at %) was immobilized onto the titanium substrate by a magnesium plasma immersion ion implantation (Mg-PIII) technique. Mg-PIII treatments did not alter surface topographies of the original titanium substrate but improved its hydrophilicity. The in vitro study including cell viability, adhesion, proliferation, migration, and real-time polymerase chain reaction assays disclosed improved adhesion, proliferation, migration, and extracellular matrix remodeling abilities of human gingival fibroblasts (HGFs) on the magnesium-doped titanium. The results of western blot suggested that the Mg-modified titanium induced the phosphorylation of AKT through the activation of PI3K. Our results revealed that magnesium-doping would potentially enhance soft tissue sealings by promoting cellular functions of HGFs in a dose-dependent manner, boding well for its applications on surfaces of implant necks in early peri-implant soft tissue integrations.

[Study on the protective mechanism of autophagy on cartilage by magnesium sulfate]

Objective

To investigate the mechanism of magnesium sulfate in protecting rabbit cartilage by initiating autophagy.

Methods

Twenty-four adult female New Zealand rabbits were used to prepare post-traumatic osteoarthritis (PTOA) models by anterior cruciate ligament transection. Then, the PTOA models were randomly divided into PTOA group, distilled water group, and magnesium sulfate group, with 8 rabbits in each group. Immediately after operation, the distilled water group and the magnesium sulfate group were injected with 0.5 mL distilled water and 20 mmol/L magnesium sulfate solution in the joint cavity 3 times a week for 4 weeks, respectively. The PTOA group was not treated. The general condition of the animals was observed after operation. After 4 weeks, the expressions of tumor necrosis factor α (TNF-α) and collagen typeⅡ in the joint fluid and the expression of collagen type Ⅱ in venous blood were detected by ELISA assay. The protein expressions of transient receptor potential channel vanilloid 5 (TRPV5) and microtubule associated protein 1 light chain 3 (LC3; LC3-Ⅱ/LC3-Ⅰ) in femoral cartilage were detected by Western blot. The mRNA expressions of interleukin 1β (IL-1β), TNF-α, matrix metalloproteinases 3 (MMP-3) in synovial tissue and collagen type Ⅱ, Aggrecan (AGN), SOX9 in cartilage tissue were detected by real-time fluorescence quantitative PCR. Cartilage tissue sections were stained with HE staining, Masson staining, and Alcian blue staining and scored according to the modified histological osteoarthritis (OA) score.

Results

All animals survived until the experiment was completed. Compared with the other two groups, the expression of TNF-α in joint effusion and collagen type Ⅱ in joint effusion and venous blood were decreased in magnesium sulfate group; the protein expression of TRPV5 decreased, and the ratio of LC3-Ⅱ/LC3-Ⅰ increased significantly; the mRNA expressions of IL-1β, TNF-α, and MMP-3 in synovial tissue were decreased, and the mRNA expressions of collagen type Ⅱ, AGN, and SOX9 in cartilage tissue were increased; OA scores also decreased significantly. All differences were statistically significant ( P<0.05). There was no significant difference in the above indicators between the PTOA group and the distilled water group ( P>0.05).

Conclusion

Intra-articular injection of magnesium sulfate can reduce intra-articular inflammation, reduce the loss of collagen type Ⅱ and AGN, and is beneficial to cartilage regeneration in rabbits. The mechanism may be related to the initiation of chondroautophagy by inhibiting the calcium channel TRPV5.

Effects of different concentrations of type-I collagen hydrogel on the growth and differentiation of chondrocytes

The objective of this study was to analyze the effects of type-I collagen hydrogel of different concentrations on the growth and differentiation of rabbit chondrocytes. Articular cartilage from New Zealand white rabbits was harvested and cultured. Second-generation chondrocytes were collected for in vitro culture with 10, 7, and 5 mg/ml type-I collagen hydrogel, respectively (denoted as groups A, B, and C). After in vitro culture for 1 day, chondrocytes were stained with fluorescein diacetate (FDA)/propidium iodide (PI), and cell viability was observed by laser confocal microscopy. After in vitro culture for 14 days, the histological patterns were observed by H&E and toluidine blue staining. The expression of chondrocyte-related genes were measured by real-time quantitative RT-PCR. After in vitro culture for 1 day, FDA/PI staining showed that the cell density of group A was significantly higher than that of group B and C. After in vitro culture for 14 days, H&E staining showed that chondrocytes showed obvious aggregation in group A, partial proliferation and aggregation in group B, and uniform distribution in group C. Toluidine blue staining showed that chondrocytes in group A had aggregation areas and some were stained purple-red, fewer chondrocytes were aggregated with different staining around them in group B, and the aggregation of chondrocytes was not obvious. However, the distribution of chondrocytes was uniform with different staining in group C. After in vitro culture for 2 weeks, the levels of polymerized proteoglycan and type-II collagen mRNA were not significantly different between the three groups (P>0.05). The levels of type-I collagen, type-X collagen, and Sox9 mRNA in group A were significantly higher than those in group B and C (P<0.05). In conclusion, high concentration type-I collagen hydrogel can promote chondrocyte fibrosis and upregulation of type-I collagen, type-X collagen, and Sox9 mRNA.

Analgesic effect and safety of single-dose intra-articular magnesium after arthroscopic surgery: a systematic review and meta-analysis

To examine the analgesic effect and safety of single-dose intra-articular (IA) magnesium (Mg) after arthroscopic surgery. Pubmed, Embase and Cochrane library were searched through in January 2016. Eight RCTs and eight experimental studies were included. The IA Mg exhibited a significantly lower pain score when compared with placebo (MD, -0.41, 95% CI, -0.78 to -0.05, p = 0.03). There was no significant difference between Mg and bupivacaine in terms of pain relief and the time to first analgesic request. Furthermore, statistically significant differences both in pain score (MD, -0.62, 95% CI, -0.81 to -0.42, p < 0.00001) and time to first analgesic request (MD, 6.25, 95% CI, 5.22 to 7.29, p < 0.00001) were observed between Mg plus bupivacaine and bupivacaine alone. There was no statistically significant difference among the various groups with respect to adverse reactions. Most of the included in vitro studies reported the chondrocyte protective effect of Mg supplementation. There were also two in vivo studies showing the cartilage protective effect of IA Mg. The single-dose IA Mg following arthroscopic surgery was effective in pain relief without increasing adverse reactions, and it could also enhance the analgesic effect of bupivacaine. In addition, Mg seemed to possess the cartilage or chondrocyte protective effect based on experimental studies.