Alterations in growth plate and articular cartilage morphology are associated with reduced SOX9 localization in the magnesium-deficient rat

The Biomimetics of Mg2+-Concentration-Resolved Microenvironment for Bone and Cartilage Repairing Materials Design

With the increase in population aging, the tendency of osteochondral injury will be accelerated, and repairing materials are increasingly needed for the optimization of the regenerative processes in bone and cartilage recovery. The local environment of the injury sites and the deficiency of Mg2+ retards the repairing period via inhibiting the progenitor osteogenesis and chondrogenesis cells’ recruitment, proliferation, and differentiation, which results in the sluggish progress in the osteochondral repairing materials design. In this article, we elucidate the Mg2+-concentration specified effect on the cell proliferation, osteochondral gene expression, and differentiation of modeling chondrocytes (extracted from New Zealand white rabbit) and osteoblasts (MC3T3-E1). The concentration of Mg2+ in the culture medium affects the proliferation, chondrogenesis, and osteogenesis: (i) Appropriate concentrations of Mg2+ promote the proliferation of chondrocytes (1.25−10.0 mM) and MC3T3-E1 cells (2.5−30.0 mM); (ii) the optimal concentration of Mg2+ that promotes the gene expression of noncalcified cartilage is 15 mM, calcified cartilage 10 mM, and subchondral bone 5 mM, respectively; (iii) overdosed Mg2+ leads to the inhibition of cell activity for either chondrocytes (>20 mM) or osteoblasts (>30 mM). The biomimetic elucidation for orchestrating the allocation of gradient concentration of Mg2+ in accordance of the physiological condition is crucial for designing the accurate microenvironment in osteochondral injury defects for optimization of bone and cartilage repairing materials in the future.

Proton pump inhibitor therapy and risk of knee replacement surgery: a general population-based cohort study

OBJECTIVE

Proton pump inhibitors (PPIs) are among the most commonly used medications for patients with osteoarthritis (OA). Various types of PPIs have different impacts on lowering serum magnesium level that may affect knee OA progression. We aimed to compare the risk of clinically relevant endpoint of knee replacement (KR) among initiators of five different PPIs with that among histamine-2 receptor antagonist (H2RA) initiators.

DESIGN

Among patients with knee OA (≥50 years) in The Health Improvement Network database in the UK we conducted five sequential propensity-score matched cohort studies to compare the risk of KR over 5-year among patients who initiated omeprazole (n = 2,672), pantoprazole (n = 664), lansoprazole (n = 3,747), rabeprazole (n = 751), or esomeprazole (n = 827) with those who initiated H2RA.

RESULTS

The prevalence of PPI prescriptions among participants with knee OA increased from 12.7% in 2000-44.0% in 2017. Two-hundred-and-seventy-four KRs (30.8/1,000 person-years) occurred in omeprazole initiators and 230 KRs (25.4/1,000 person-years) in H2RA initiators. Compared with H2RA initiators, the risk of KR was 21% higher in omeprazole initiators (hazard ratio [HR] = 1.21,95% confidence interval [CI]:1.01-1.44). Similar results were observed when pantoprazole use was compared with H2RA use (HR = 1.38,95%CI:1.00-1.90). No such an increased risk of KR was observed among lansoprazole (HR = 1.06,95%CI:0.92-1.23), rabeprazole (HR = 0.97,95%CI:0.73-1.30), or esomeprazole (HR = 0.83,95%CI:0.60-1.15) initiators compared with that among H2RA initiators.

CONCLUSIONS

In this population-based cohort study, initiation of omeprazole or pantoprazole use was associated with a higher risk of KR than initiation of H2RA use. This study raises concern regarding an unexpected risk of omeprazole and pantoprazole on accelerating OA progression.

Research status of biodegradable metals designed for oral and maxillofacial applications: A review

The oral and maxillofacial regions have complex anatomical structures and different tissue types, which have vital health and aesthetic functions. Biodegradable metals (BMs) is a promising bioactive materials to treat oral and maxillofacial diseases. This review summarizes the research status and future research directions of BMs for oral and maxillofacial applications. Mg-based BMs and Zn-based BMs for bone fracture fixation systems, and guided bone regeneration (GBR) membranes, are discussed in detail. Zn-based BMs with a moderate degradation rate and superior mechanical properties for GBR membranes show great potential for clinical translation. Fe-based BMs have a relatively low degradation rate and insoluble degradation products, which greatly limit their application and clinical translation. Furthermore, we proposed potential future research directions for BMs in the oral and maxillofacial regions, including 3D printed BM bone scaffolds, surface modification for BMs GBR membranes, and BMs containing hydrogels for cartilage regeneration, soft tissue regeneration, and nerve regeneration. Taken together, the progress made in the development of BMs in oral and maxillofacial regions has laid a foundation for further clinical translation.

Intra-articular injection of magnesium chloride attenuates osteoarthritis progression in rats

OBJECTIVE

To explore the effects of Mg²⁺ on the expression of osteoarthritic markers in human cartilage and synovium tissue explants. To investigate the therapeutic effect of intra-articular injection of Mg²⁺ in an established rat OA (Osteoarthritis) model of anterior cruciate ligament transection with partial medial meniscectomy (ACLT + PMM).

DESIGN

Human cartilage and synovium explants were collected from total knee replacement surgeries and incubated with MgCl₂ (20 mmol/L) in vitro. A rat OA model was established by ACLT + PMM surgery in 450-500 g male Sprague Dawley (SD) rats. To select the optimal dose, intra-articular injections of MgCl₂ (0.05, 0.5, 5 mol/L) were performed at 4 weeks after the surgery every 3 days for 2 weeks. The effect of optimized MgCl₂ was further determined by histology, immunohistochemistry, and quantitative real-time polymerase chain reaction.

RESULTS

The expressions of osteoarthritic markers in human cartilage and synovium explants were inhibited by Mg²⁺in vitro. Immunohistochemical analysis further suggested the inhibitory effects of Mg²⁺ on the expression of MMP-13 and IL-6 in the human tissue explants. Cartilage degeneration and synovitis in ACLT + PMM rats were significantly improved by intra-articular injections of Mg²⁺ (0.5 mol/L). Immunohistochemical analysis also showed the regulatory effects of Mg²⁺ on osteoarthritic markers in both cartilage and synovium in rats, consistent with in vitro results.

CONCLUSION

Intra-articular injections of Mg²⁺ at 0.5 mol/L attenuate the progression of OA in the ACLT + PMM rat model. Such effect was at least in part explained by the promotion of cartilage matrix synthesis and the suppression of synovial inflammation.

[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.

Magnesium enhances the chondrogenic differentiation of mesenchymal stem cells by inhibiting activated macrophage-induced inflammation

Magnesium deficiency increases the generation of pro-inflammatory cytokines, which is consistently accompanied by the sensitization of cells such as neutrophils, macrophages and endothelial cells. We investigated the potential of magnesium to regulate macrophage polarization and macrophage-induced inflammation with or without lipopolysaccharide (LPS) and interferon-γ (IFN-γ) activation and further elucidated whether these effects impact the inhibitory functions of activated macrophage-induced inflammation on cartilage regeneration. The results showed that magnesium inhibited the activation of macrophages, as indicated by a significant reduction in the percentage of CCR7-positive cells, while the percentage of CD206-positive cells decreased to a lesser degree. After activation, both pro-inflammatory and anti-inflammatory cytokines were down-regulated at the mRNA level and certain cytokines (IL-1β, IL-6 and IL-10) were decreased in the cell supernatant with the addition of magnesium. Moreover, magnesium decreased the nuclear translocation and phosphorylation of nuclear factor-κB (NF-κB) to impede its activation. A modified micromass culture system was applied to assess the effects of activated macrophage-conditioned medium with or without magnesium treatment on the chondrogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). Magnesium enhanced the chondrogenic differentiation of hBMSCs by reversing the adverse effects of activated macrophage-induced inflammation.

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.

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.

Relationship between Serum Magnesium Concentration and Radiographic Knee Osteoarthritis

OBJECTIVE

To establish whether there is a relationship between serum magnesium (Mg) concentration and radiographic knee osteoarthritis (OA).

METHODS

There were 2855 subjects in this cross-sectional study. Serum Mg concentration was measured using the chemiluminescence method. Radiographic OA of the knee was defined as changes consistent with Kellgren-Lawrence (K-L) grade 2 on at least 1 side. Mg concentration was classified into 1 of 4 quartiles: ≤ 0.87, 0.88-0.91, 0.92-0.96, or ≥ 0.97 mmol/l. Multivariable logistic analysis was used to test the association between serum Mg and radiographic knee OA after adjustment for potentially confounding factors. The OR with 95% CI for the association between radiographic knee OA and serum Mg concentration were calculated for each quartile. The quartile with the lowest value was regarded as the reference category.

RESULTS

Significant association between serum Mg concentration and radiographic knee OA was observed in the model after adjustment for age, sex, and body mass index, as well as in the multivariable model. The multivariable-adjusted OR (95% CI) for radiographic knee OA in the second, third, and fourth serum Mg concentration quartiles were 0.90 (95% CI 0.71-1.13), 0.92 (95% CI 0.73-1.16), and 0.72 (95% CI 0.57-0.92), respectively, compared with the lowest (first) quartile. A clear trend (p for trend was 0.01) was observed. The relative odds of radiographic knee OA was decreased by 0.72 times in the fourth serum Mg quartile compared with the lowest quartile.

CONCLUSION

Serum Mg concentration may have an inverse relationship with radiographic OA of the knee.

Association between Dietary Magnesium Intake and Radiographic Knee Osteoarthritis

Objective

To examine the cross-sectional associations between dietary magnesium (Mg) intake and radiographic knee osteoarthritis (OA), joint space narrowing (JSN), and osteophytes (OST) respectively.

Methods

A total of 1626 subjects were included in the study. Dietary intake was assessed using a validated semi-quantitative food frequency questionnaire. Radiographic knee OA was defined as Kellgren-Lawrence (K-L) Grade 2 in at least one leg. JSN and OST were assessed individually according to the Osteoarthritis Research Society International (OARSI) atlas. A multivariable logistic analysis model was applied to test the various associations after adjusting for potentially confounding factors.

Results

The relative odds of radiographic knee OA were decreased by 0.53 times in the third quintile of Mg intake [odds ratio (OR) 0.53, 95% confidence interval (CI) 0.28–1.01], 0.40 times in the fourth quintile (OR 0.40, 95% CI 0.17–0.94) and 0.34 times in the fifth quintile (OR 0.34, 95% CI 0.11–1.00) compared with those in the lowest quintile, while P for trend was 0.111. The relative odds of JSN were decreased by 0.49 times in the third quintile of Mg intake (OR 0.49, 95% CI 0.28–0.88) and 0.37 times in the fifth quintile (OR 0.37, 95% CI 0.14–0.98) compared with those in the lowest quintile, while P for trend was 0.088. There was no significant relationship between dietary Mg intake and the presence of OST.

Conclusions

The findings of this cross-sectional study indicate that Mg intake is inversely associated with radiographic knee OA and JSN. It supports potential role of Mg in the prevention of knee OA.

Level of Evidence

LevelIII, cross-sectional study.

Magnesium in man: implications for health and disease

Magnesium (Mg(2+)) is an essential ion to the human body, playing an instrumental role in supporting and sustaining health and life. As the second most abundant intracellular cation after potassium, it is involved in over 600 enzymatic reactions including energy metabolism and protein synthesis. Although Mg(2+) availability has been proven to be disturbed during several clinical situations, serum Mg(2+) values are not generally determined in patients. This review aims to provide an overview of the function of Mg(2+) in human health and disease. In short, Mg(2+) plays an important physiological role particularly in the brain, heart, and skeletal muscles. Moreover, Mg(2+) supplementation has been shown to be beneficial in treatment of, among others, preeclampsia, migraine, depression, coronary artery disease, and asthma. Over the last decade, several hereditary forms of hypomagnesemia have been deciphered, including mutations in transient receptor potential melastatin type 6 (TRPM6), claudin 16, and cyclin M2 (CNNM2). Recently, mutations in Mg(2+) transporter 1 (MagT1) were linked to T-cell deficiency underlining the important role of Mg(2+) in cell viability. Moreover, hypomagnesemia can be the consequence of the use of certain types of drugs, such as diuretics, epidermal growth factor receptor inhibitors, calcineurin inhibitors, and proton pump inhibitors. This review provides an extensive and comprehensive overview of Mg(2+) research over the last few decades, focusing on the regulation of Mg(2+) homeostasis in the intestine, kidney, and bone and disturbances which may result in hypomagnesemia.

Regional differences in elements of human peroneus longus tendons

Many studies have been performed on the structure, molecular composition, and biochemical properties of tendons. However, comparatively little research has been conducted on the content of various trace elements within tendons. Six elements were analyzed in four regions of the peroneus longus tendon: the tensional part of the tendon immediately proximal to the lateral malleolus (region A), the compressive region of the tendon in contact with the lateral malleolus (region B), the compressive region of the tendon in contact with the deep surface of the cuboid (region C), and the tensional part of the tendon between the cuboid and first metatarsal, to which the tendon is attached (region D). Regions B and C are wraparound regions. The calcium content was higher in region C (2.10 ± 0.93 mg/g) than in both regions A (1.25 ± 0.51 mg/g) and D (1.43 ± 0.41 mg/g) (p < 0.05), indicating that it is likely related to regional differences in cartilage degeneration. The phosphorus content was also higher in region C, possibly because of low alkaline phosphatase activity in this region. The sulfur content was higher in the wraparound regions (region B: 0.98 ± 0.09 mg/g, region C: 1.24 ± 0.19 mg/g) than in both regions A (0.83 ± 0.11 mg/g) and D (0.83 ± 0.1 mg/g) (p < 0.01); sulfur content is thought to be influenced by tendon-bone compression. Finally, the magnesium content in the wraparound regions was also higher, which is probably related to a higher level of fibrocartilage. No significant relationships were found with regard to zinc or iron. Overall, the findings of the present study indicate that element contents are related to function and anatomical differences in tendons, and that they may even vary within the same tendon.

Articular cartilage and growth plate defects are associated with chondrocyte cytoskeletal abnormalities in Tg737orpk mice lacking the primary cilia protein polaris

Primary cilia are highly conserved organelles found on almost all eukaryotic cells. Tg737(orpk) (orpk) mice carry a hypomorphic mutation in the Tg737 gene resulting in the loss of polaris, a protein essential for ciliogenesis. Orpk mice have an array of skeletal patterning defects and show stunted growth after birth, suggesting defects in appositional and endochondral development. This study investigated the association between orpk tibial long bone growth and chondrocyte primary cilia expression using histomorphometric and immunohistochemical analysis. Wild-type chondrocytes throughout the developing epiphysis and growth plate expressed primary cilia, which showed a specific orientation away from the articular surface in the first 7-10 cell layers. In orpk mice, primary cilia were identified on very few cells and were significantly shorter. Orpk chondrocytes also showed significant increases in cytoplasmic tubulin, a likely result of failed ciliary assembly. The growth plates of orpk mice were significantly smaller in length and width, with marked changes in cellular organization in the presumptive articular cartilage, proliferative and hypertrophic zones. Cell density at the articular surface and in the hypertrophic zone was significantly altered, suggesting defects in both appositional and endochondral growth. In addition, orpk hypertrophic chondrocytes showed re-organization of the F-actin network into stress fibres and failed to fully undergo hypertrophy, while there was a marked reduction in type X collagen sequestration. These data suggest that failure to form a functional primary cilium affects chondrocyte differentiation and results in delayed chondrocyte hypertrophy within the orpk growth plate.

Dietary magnesium reduction to 25% of nutrient requirement disrupts bone and mineral metabolism in the rat

Low dietary magnesium (Mg) may be a risk factor for osteoporosis. In animals, severe Mg deficiency (0.04% of nutrient requirement [NR]) results in bone loss. We have also found that a more moderate dietary Mg restriction (10% of NR) also resulted in loss of bone. We now report the effect of Mg intake of 25% NR on bone and mineral metabolism in the rat. Serum Mg, Ca, PTH, 1,25(OH)2-vitamin D, alkaline phosphatase, osteocalcin, and pyridinoline were measured at 2, 4, and 6 months in control and Mg-deficient animals. Femurs and tibias were collected for mineral content, micro-computerized tomography, histomorphometry, and immunocytochemical localization. Profound Mg deficiency developed as assessed by marked hypomagnesemia and 27% reduction in bone Mg content. Serum calcium was not significantly different between groups. Mg depletion resulted in a significantly lower serum PTH concentrations. Serum 1,25(OH)2-vitamin D was also significantly lower. No difference was noted in markers of bone turnover. Histomorphometry and micro-computerized tomography demonstrated decreased bone volume and trabecular thickness. No difference was observed for osteoclast or osteoblast number. Inflammatory cytokines may contribute to bone loss. We found that immunocytochemical localization of TNFalpha in osteoclasts was increased 138-150%. This increase in TNFalpha may be due to increased substance P as it was found to be elevated from 179% to 432%. These data demonstrate that Mg intake of 25% NR in the rat causes lower bone mass which may be related to increased release of substance P and TNFalpha.

Magnesium deficiency and osteoporosis: animal and human observations

Although osteoporosis is a major health concern for our growing population of the elderly, there continues to be a need for well-designed clinical and animal studies on the link between dietary magnesium (Mg) intake and osteoporosis. Relatively few animal studies have assessed the skeletal and hormonal impact of long-term low Mg intake; however, these studies have demonstrated that Mg deficiency results in bone loss. Potential mechanisms include a substance P-induced release of inflammatory cytokines as well as impaired production of parathyroid hormone and 1,25-dihydroxyvitamin D. Abnormal mineralization of bones may also contribute to skeletal fragility. Clinical studies have often varied greatly in study design, subject age, menopausal status and outcome variables that were assessed. Most studies focused on female subjects, thus pointing to the great need for studies on aging males. According to the U.S. Department of Agriculture, the mean Mg intake for males and females is 323 and 228 mg/day, respectively. These intake levels suggest that a substantial number of people may be at risk for Mg deficiency, especially if concomitant disorders and/or medications place the individual at further risk for Mg depletion. In this paper, we will review animal and human evidence of the association of Mg deficiency with osteoporosis and explore possible mechanisms by which this may occur.