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

Advancing Scaffold-Assisted Modality for In Situ Osteochondral Regeneration: A Shift From Biodegradable to Bioadaptable

Over the decades, the management of osteochondral lesions remains a significant yet unmet medical challenge without curative solutions to date. Owing to the complex nature of osteochondral units with multi-tissues and multicellularity, and inherently divergent cellular turnover capacities, current clinical practices often fall short of robust and satisfactory repair efficacy. Alternative strategies, particularly tissue engineering assisted with biomaterial scaffolds, achieve considerable advances, with the emerging pursuit of a more cost-effective approach of in situ osteochondral regeneration, as evolving toward cell-free modalities. By leveraging endogenous cell sources and innate regenerative potential facilitated with instructive scaffolds, promising results are anticipated and being evidenced. Accordingly, a paradigm shift is occurring in scaffold development, from biodegradable and biocompatible to bioadaptable in spatiotemporal control. Hence, this review summarizes the ongoing progress in deploying bioadaptable criteria for scaffold-based engineering in endogenous osteochondral repair, with emphases on precise control over the scaffolding material, degradation, structure and biomechanics, and surface and biointerfacial characteristics, alongside their distinguished impact on the outcomes. Future outlooks of a highlight on advanced, frontier materials, technologies, and tools tailoring precision medicine and smart healthcare are provided, which potentially paves the path toward the ultimate goal of complete osteochondral regeneration with function restoration.

A Novel Scaffold of Icariin/Porous Magnesium Alloy-Repaired Knee Cartilage Defect in Rat by Wnt/β-Catenin Signaling Pathway

Cartilage defects caused by joint diseases are difficult to treat clinically. Tissue engineering materials provide a new means to promote the repair of cartilage defects. The purpose of this study is to design a novel scaffold of porous magnesium alloy loaded with icariin and sustained release in order to explore the effect and possible mechanism of this scaffold in repairing SD rat knee articular cartilage defect. We constructed a novel type of icariin/porous magnesium alloy scaffold, observed the structure of the scaffold by electron microscope, detected the drug release of icariin in the scaffold and the biological safety, and established an animal model of cartilage defect in the femoral intercondylar fossa of the knee joint in rats; the scaffold was placed in the defect. After 12 weeks of repair, the rat knee articular cartilage repair was evaluated by gross specimens and micro-CT, HE, safranin O-fast green, and toluidine blue staining combined with the modified Mankin's score. The protein expressions of the Wnt/β-catenin signaling pathway-related factors (β-catenin, Wnt5a, Wnt1, sFRP1) and chondrogenic differentiation-related factors (Sox9, Aggrecan, Col2α1) were detected by immunohistochemical staining. We found that the novel scaffold of icariin/porous magnesium alloy can release icariin slowly and has biosafety in rats. Compared with other groups, icariin/porous magnesium alloy can significantly promote the repair of cartilage defects and the expressions of β-catenin, Wnt5a, Wnt1, Sox9, Aggrecan, and Col2α1 (P < 0.05). This novel scaffold can promote the repair of rat knee cartilage defects, and this process may be achieved by activating the Wnt/β-catenin signaling pathway.

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.

Cardiovascular and All-Cause Mortality Is Affected by Serum Magnesium and Diet Pattern in a Cohort of Dialysis Patients

Background: Hypomagnesaemia is associated with an increased overall mortality in patients with chronic kidney disease on dialysis (CKD-5D). Mediterranean-style diet (MD), having a high magnesium content, can serve as a form of dietary magnesium supplementation. We examined whether there is a potential link between increased Mediterranean Diet score (MDS) and elevated serum magnesium (sMg) to assess its impact on reducing mortality risk in CKD-5D patients. Methods: In this multi-center prospective observational study, 117 CKD-5D patients (66 on hemodialysis and 51 on peritoneal dialysis) with a mean age of 62 ± 15 years were studied for a median follow-up period of 68 months. After baseline assessment, including measurement of sMg and MDS, all patients were followed up for cardiovascular (CV) and all-cause mortality. Results: Forty deaths occurred, 58% of which were cardiovascular. Patients who were above the median value of sMg (2.2 mg/dL) had a 66% reduction in CV (crude HR, 0.34; 95% CI, 0.11-0.70), and 49% reduction in all-cause (crude HR, 0.51; 95% CI, 0.27-0.96) mortality, even after adjustment for age, malnutrition inflammation score, left ventricular mass index, peripheral vascular disease and diabetes. Similar results were obtained when sMg was analyzed as a continuous variable. sMg was associated directly with MDS (r = 0.230; p = 0.012). Conclusions: Higher sMg levels are strongly and independently associated with reduced CV and all-cause mortality in CKD-5D patients. A strong correlation exists between MDS and sMg. Elevated sMg levels, achieved through MD adherence, can significantly reduce CV mortality, implicating MD as a mediator of the association between sMg and CV mortality.

Highly Stable Amorphous (Pyro)phosphate Aggregates: Pyrophosphate as a Carrier for Bioactive Ions and Drugs in Bone Repair Applications

Pyrophosphate is widely used as an iron supplement because of its excellent complexation and hydrolysis ability; however, there are few reports on the use of pyrophosphate in active ionophores for bone repair. In this research, we proposed a simple and efficient ultrasonic method to prepare magnesium-calcium (pyro)phosphate aggregates (AMCPs). Due to strong hydration, AMCPs maintain a stable amorphous form even at high temperatures (400 °C). By changing the molar ratio of calcium and magnesium ions, the content of calcium and magnesium ions can be customized. AMCPs had surface negativity and complexing ability that realized the controlled release of ions (Ca2+, Mg2+, and P) and drugs (such as doxorubicin) over a long period. Pyrophosphate gave it an excellent bacteriostatic effect. Increasingly released Mg2+ exhibited improved bioactivity though the content of Ca2+ decreased. While Mg2+ content was regulated to 15 wt %, it performed significantly enhanced stimulation on the proliferation, attachment, and differentiation (ALP activity, calcium nodules, and the related gene expression of osteogenesis) of mouse embryo osteoblast precursor cells (MC3T3-E1). Furthermore, the high content of Mg2+ also effectively promoted the proliferation, attachment, and migration of human umbilical vein endothelial cells (HUVECs) and the expression of angiogenic genes. In conclusion, pyrophosphate was an excellent carrier for bioactive ions, and the AMCPs we prepared had a variety of active functions for multiscenario bone repair applications.

Empowering Cartilage Restructuring with Biodegradable Magnesium Doped-Silicon Based-Nanoplatforms: Sustained Delivery and Enhanced Differentiation Potential

Background

Cartilage-related diseases, such as hypoplastic chondrodysplasia a rare genetic disorder that affects newborns, causing abnormal cartilage development and restricted skeletal growth. However, the development of effective treatment strategies for chondrodysplasia still faces significant challenges due to limitations in the controlled drug delivery, biocompatibility, and biodegradability of nanomedicines.

Methods

A biodegradable magnesium doped-silicon based-nanoplatforms based on silicon nanoparticles (MON) was constructed. Briefly, the MON was modified with sulfhydryl groups using MPTMS to form MOS. Further engineering of MOS was achieved by incorporating Mg2+ ions through the "dissolution-regrowth" method, resulting in MMOS. Ica was effectively loaded into the MMOS channels, and HA was anchored on the surface of MOS to obtain MMOS-Ica@HA nanoplatforms. Additionally, in vitro cell experiments and in vivo zebrafish embryo models were used to evaluate the effect of the nanoplatforms on cartilage differentiation or formation and the efficiency of treating chondrodysplasia.

Results

A series of characterization tests including TEM, SEM, DLS, XPS, EDX, and BET analysis validate the successful preparation of MOS-Ica@HA nanoplatforms. The prepared nanoplatforms show excellent dispersion and controllable drug release behavior. The cytotoxicity evaluation reveals the good biocompatibility of MOS-Ica@HA due to the sustained and controllable release of Ica. Importantly, the presence of Ica and Mg component in MOS-Ica@HA significantly promote chondrogenic differentiation of BMSCs via the Smad5/HIF-1α signaling pathway. In vitro and in vivo experiments confirmed that the nanoplatforms improved chondrodysplasia by promoting cartilage differentiation and formation.

Conclusion

The findings suggest the potential application of the developed biodegradable MMOS-Ica@HA nanoplatforms with acceptable drug loading capacity and controlled drug release in chondrodysplasia treatment, which indicates a promising approach for the treatment of chondrodysplasia.

Low extracellular magnesium induces phenotypic and metabolic alterations in C2C12-derived myotubes

Magnesium (Mg) has a pivotal role in upholding skeletal muscle health and optimizing performance. Its deficiency decreases muscle strength, and an association has been reported between Mg intake and sarcopenia. To gain a comprehensive understanding of the repercussions arising from low Mg concentrations on muscle behavior, we employed an in vitro model utilizing C2C12-derived myotubes. Myotubes cultured in low Mg show a significant reduction of thickness and a concomitant down-regulation of myosin heavy chain (MyHC), Myog and Myomixer. In parallel, myotubes shape their metabolism. Glycolysis is inhibited and beta-oxidation increases. These metabolic changes are consistent with the increase of MyHC I (slow) vs. MyHC II (fast) expression. We identified an essential player in these changes, namely nitric oxide (NO), as the increase in NO production appeared to orchestrate the observed modifications in myotube behavior and metabolism under low Mg conditions. Understanding these underlying mechanisms may pave the way for targeted interventions to ameliorate muscle-related conditions associated with Mg deficiency and contribute to enhancing overall muscle health and function.

A hydrogel reservoir as a self-contained nucleus pulposus cell delivery vehicle for immunoregulation and repair of degenerated intervertebral disc

The strategies for modulating the local inflammatory microenvironment to inhibit intervertebral disc degeneration (IVDD) have garnered significant interest in recent years. In this study, we developed a "self-contained" injectable hydrogel capable of storing Mg2+ while carrying nucleus pulposus (NP) cells, with the aim of inhibiting IVDD through immunoregulation. The hydrogel consists of sodium alginate (SA), poly(N-isopropylacrylamide) (PNIPAAm), silicate ceramics (SC), and NP cells. When injected into the NP site, PNIPAAm gelates instantly under body temperature, forming an interpenetrating network (IPN) hydrogel with SA. Ca2+ released from the SC can crosslink the SA in situ, forming a SA/PNIPAAm hydrogel with an interpenetrating network (IPN) encapsulating the NP cells. Moreover, inside the hydrogel, Mg2+ released from SC are effectively encapsulated and maintained at a desirable concentration. These Mg2+ facilitates the local cell matrix synthesis and promotes immunomodulation (upregulating M2 / downregulating M1 macrophage polarization), thus inhibiting the IVDD progression. The proposed hydrogel has biocompatibility and is shown to enhance the expression of collagen II (COL II) and aggrecan. The potential of the injectable hydrogel in IVD repair has also been successfully demonstrated by in vivo studies. STATEMENT OF SIGNIFICANCE.

Autophagy and apoptosis: regulatory factors of chondrocyte phenotype transition in osteoarthritis

Osteoarthritis (OA) is the main pathogenic factor in diseases that cause joint deformities. As the main manifestation of the progress of OA, cartilage degradation has been closely associated with the degeneration of chondrocytes, which is induced by inflammatory factors and other trauma factors. Autophagy and apoptosis are the main mechanisms for cells to maintain homeostasis and play crucial roles in OA. Under the influence of external environmental factors (such as aging and injury), the metabolism of cells can be altered, which may affect the extent of autophagy and apoptosis. With the progression of OA, these changes can alter the cell phenotypes, and the cells of different phenotypes display distinct differences in morphology and function. In this review, we have summarized the alteration in cell metabolism, autophagy, and the extent of apoptosis during OA progression and its effects on the cell phenotypes to provide new ideas for further research on the mechanisms of phenotypic transition and therapeutic strategies so as to reverse the cell phenotypes.

CircRNA_0026344 via miR-21 is involved in cigarette smoke-induced autophagy and apoptosis of alveolar epithelial cells in emphysema

Cigarette smoke (CS), a main source of indoor air pollution, is a primary risk factor for emphysema, and aberrant cellular autophagy is related to the pathogenesis of emphysema. Circular RNAs (circRNAs) affect the expression of mRNAs via acting as microRNA (miRNA) sponges, but their role in emphysema progression is not established. In the present investigation, CS, acting on alveolar epithelial cells, caused higher levels of miR-21, p-ERK, and cleaved-caspase 3 and led to lower levels of circRNA_0026344 and PTEN, which induced autophagy and apoptosis. miR-21 suppressed the expression of PTEN, which was involved in the regulation of autophagy and apoptosis. Further, in alveolar epithelial cells, overexpression of circRNA_0026344 blocked cigarette smoke extract (CSE)-induced autophagy and apoptosis, but this blockage was reversed by upregulation of miR-21 with a mimic. These results demonstrated that, in alveolar epithelial cells, CS decreases circRNA_0026344 levels, which sponge miR-21 to inhibit the miR-21 target, PTEN, which, in turn, activates ERK and thereby promotes autophagy and apoptosis, leading to emphysema. Thus, for emphysema, circRNA_0026344 regulates the PTEN/ERK axis by sponging miR-21, which is associated with the CS-induced autophagy and apoptosis of alveolar epithelial cells. In sum, the present investigation identifies a novel mechanism for CS-induced emphysema and provides information useful for the diagnosis and treatment of CS-induced emphysema.

Incorporation of Magnesium Ions into an Aptamer-Functionalized ECM Bioactive Scaffold for Articular Cartilage Regeneration

The regeneration and reconstruction of articular cartilage (AC) after a defect are often difficult. The key to the treatment of AC defects lies in regeneration of the defect site and regulation of the inflammatory response. In this investigation, a bioactive multifunctional scaffold was formulated using the aptamer Apt19S as a mediator for mesenchymal stem cell (MSC)-specific recruitment and the enhancement of cellular chondrogenic and inflammatory regulation through the incorporation of Mg²⁺. Apt19S, which can recruit MSCs in vitro and in vivo, was chemically conjugated to a decellularized cartilage extracellular matrix (ECM)-lysed scaffold. The results from in vitro experiments using the resulting scaffold demonstrated that the inclusion of Mg²⁺ could stimulate not only the chondrogenic differentiation of synovial MSCs but also the increased polarization of macrophages toward the M2 phenotype. Additionally, Mg²⁺ inhibited NLRP3 inflammasome activation, thereby decreasing chondrocyte pyroptosis. Subsequently, Mg²⁺ was incorporated into the bioactive multifunctional scaffold, and the resulting scaffold promoted cartilage regeneration in vivo. In conclusion, this study confirms that the combination of Mg²⁺ and aptamer-functionalized ECM scaffolds is a promising strategy for AC regeneration based on in situ tissue engineering and early inflammatory regulation.

The role of autophagy in bone metabolism and clinical significance

The skeletal system is the basis of the vertebral body composition, which affords stabilization sites for muscle attachment, protects vital organs, stores mineral ions, supplies places to the hematopoietic system, and participates in complex endocrine and immune system. Not surprisingly, bones are constantly reabsorbed, formed, and remodeled under physiological conditions. Once bone metabolic homeostasis is interrupted (including inflammation, tumors, fractures, and bone metabolic diseases), the body rapidly initiates bone regeneration to maintain bone tissue structure and quality. Macroautophagy/autophagy is an essential metabolic process in eukaryotic cells, which maintains metabolic energy homeostasis and plays a vital role in bone regeneration by controlling molecular degradation and organelle renewal. One relatively new observation is that mesenchymal cells, osteoblasts, osteoclasts, osteocytes, chondrocytes, and vascularization process exhibit autophagy, and the molecular mechanisms and targets involved are being explored and updated. The role of autophagy is also emerging in degenerative diseases (intervertebral disc degeneration [IVDD], osteoarthritis [OA], etc.) and bone metabolic diseases (osteoporosis [OP], osteitis deformans, osteosclerosis). The use of autophagy regulators to modulate autophagy has benefited bone regeneration, including MTOR (mechanistic target of rapamycin kinase) inhibitors, AMPK activators, and emerging phytochemicals. The application of biomaterials (especially nanomaterials) to trigger autophagy is also an attractive research direction, which can exert superior therapeutic properties from the material-loaded molecules/drugs or the material's properties such as shape, roughness, surface chemistry, etc. All of these have essential clinical significance with the discovery of autophagy associated signals, pathways, mechanisms, and treatments in bone diseases in the future.Abbreviations: Δψm: mitochondrial transmembrane potential AMPK: AMP-activated protein kinase ARO: autosomal recessive osteosclerosis ATF4: activating transcription factor 4 ATG: autophagy-related β-ECD: β-ecdysone BMSC: bone marrow mesenchymal stem cell ER: endoplasmic reticulum FOXO: forkhead box O GC: glucocorticoid HIF1A/HIF-1α: hypoxia inducible factor 1 subunit alpha HSC: hematopoietic stem cell HSP: heat shock protein IGF1: insulin like growth factor 1 IL1B/IL-1β: interleukin 1 beta IVDD: intervertebral disc degradation LPS: lipopolysaccharide MAPK: mitogen-activated protein kinase MSC: mesenchymal stem cell MTOR: mechanistic target of rapamycin kinase NP: nucleus pulposus NPWT: negative pressure wound therapy OA: osteoarthritis OP: osteoporosis PTH: parathyroid hormone ROS: reactive oxygen species SIRT1: sirtuin 1 SIRT3: sirtuin 3 SQSTM1/p62: sequestosome 1 TNFRSF11B/OPG: TNF receptor superfamily member 11b TNFRSF11A/RANK: tumor necrosis factor receptor superfamily, member 11a TNFSF11/RANKL: tumor necrosis factor (ligand) superfamily, member 11 TSC1: tuberous sclerosis complex 1 ULK1: unc-51 like autophagy activating kinase 1.

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.

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

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

A bionic composite hydrogel with dual regulatory functions for the osteochondral repair

Due to the avascular nature of cartilage, it is difficult to heal and regenerate spontaneously after injury. At present, tissue engineering has become a promising strategy for repairing damaged cartilage, but the use of seed cells and growth factors is limited. In addition, the importance of mechanical compatibility of scaffold materials is often ignored. In this study, osteochondral scaffold was designed as a bilayer structure with a dense γ-Polyglutamic acid/carboxymethyl chitosan/bacterial cellulose (PGA/CMCS/BC) hydrogel cartilage layer and a porous nano HA-containing PGA/CMCS/BC hydrogel osteogenic layer. In addition, bioactive ions were introduced into the hydrogel scaffold to adjust the mechanical and swelling properties of the material to match the mechanical properties of natural articular cartilage. At the same time, based on the structural characteristics of bone and cartilage, magnesium and copper ions were introduced into the double-layer hydrogel scaffold, respectively, to prepare the cartilage layer and the bone layer, which endowed the material with excellent antibacterial properties and achieved the purpose of the integrated repair of bone and cartilage. The results showed that, after adding magnesium ions, the tensile breaking strength of material was increased from 0.66 MPa to 1.37 MPa，the corresponding compression modulus of the material (strain 0-12%) increased from 0.15 MPa to 0.58 MPa whilst the maximum mass swelling rate decreased from 155% to 75%. The results of in vivo experiments show that the group with bioactive ions had a much better effect on the repair of osteochondral defects, compared with group without bioactive ions, demonstrating such double ion regulation strategy is a very practical strategy for the treatment of osteochondral defects.

Magnesium Supplementation Stimulates Autophagy to Reduce Lipid Accumulation in Hepatocytes via the AMPK/mTOR Pathway

Metabolic-associated fatty liver disease (MAFLD) (previously known as nonalcoholic fatty liver disease (NAFLD)) is a disease with high worldwide prevalence, but with limited available therapeutic interventions. Autophagy is a cell survival mechanism for clearing excess lipids in hepatocytes and affects the occurrence and development of MAFLD. In addition, some studies have shown that magnesium deficiency is common in patients with obesity and metabolic syndrome. Magnesium supplementation can effectively improve metabolism-related diseases such as obesity and fatty liver. Our study successfully constructed a cellular model of MAFLD by 1 mM free fatty acid (FFA) intervention in LO2 cells for 24 h, and there was an increase in lipid accumulation in hepatocytes after FFA intervention. Magnesium supplementation was shown to reduce lipid deposition in hepatocytes induced by FFA, and Western blotting (WB) analysis showed that magnesium supplementation could downregulate the expression of Fasn and SREBP1 and increase the expression of LPL, suggesting that magnesium can reduce lipid accumulation by reducing lipid synthesis and increasing lipid oxidation. Magnesium supplementation could affect cellular lipid metabolism by activating the AMPK/mTOR pathway to stimulate autophagy. Our results identified a relationship between magnesium and lipid accumulation in hepatocytes and showed that magnesium supplementation reduced lipid deposition in hepatocytes by activating autophagy by activating the AMPK-mTOR pathway.

Intra-Articular Magnesium Plus Bupivacaine Is the Most Effective and Safe Postoperative Analgesic Option Following Knee Arthroscopy: A Network Meta-analysis

PURPOSE

To evaluate the comparative efficacy and safety of single-dose intra-articular injection of commonly used analgesics after knee arthroscopy.

METHODS

A systematic literature review was done to search for randomized controlled trials (RCTs) published from database inception to October 1, 2020, that compared analgesics (i.e., morphine, bupivacaine, ropivacaine, and magnesium alone or in combination) with placebo or each other after knee arthroscopy. The primary outcomes were postoperative pain intensity at 2 hours and 24 hours. Secondary outcomes included the time to first analgesic request, number of patients requiring supplementary analgesics and side effects. We estimated summary standardized mean differences (SMDs) or odds ratios with 95% credible intervals (95% CrIs) using Bayesian network meta-analysis with random effects.

RESULTS

In total, 78 randomized controlled trials comprising 4,425 participants were included. Compared with placebo, magnesium plus bupivacaine was most likely to be effective in relieving pain at both 2-hour (SMD = -3.81, 95% CrI -5.28 to -2.35) and 24-hour after surgery (SMD = -2.81, 95% CrI: -4.29 to -1.30). Following was morphine plus bupivacaine (2-hour: SMD = -2.19, 95% CrI -3.05 to -1.31; 24-hour: SMD = -1.44, 95% CrI -2.14 to -0.73) and bupivacaine alone (2-hour: SMD = -1.66, 95% CrI -2.33 to -0.98; 24-hour: SMD = -0.67, 95% CrI -1.22 to -0.07); ropivacaine alone and magnesium alone were not effective on pain relief. The interval time to first analgesic request was significantly extended compared with placebo except for ropivacaine alone and magnesium alone. The number of patients requiring supplementary analgesics was reduced in all groups except ropivacaine alone. No statistically significant difference was found between any studied analgesics or placebo with regard to side effects.

CONCLUSIONS

Of 6 common postoperative intra-articular analgesics, magnesium plus bupivacaine provides the most effective pain relief without increasing short-term side effects after knee arthroscopy.

LEVEL OF EVIDENCE

Level II, meta-analysis of Level I and II studies.

Increased Wnt/β-catenin signaling contributes to autophagy inhibition resulting from a dietary magnesium deficiency in injury-induced osteoarthritis

Background

Dietary magnesium deficiency, which is common in modern diet, has been associated with osteoarthritis (OA) susceptibility. Despite this clinical association, no study has addressed if dietary magnesium deficiency accelerates OA development, especially at molecular level. This study aimed to explore aggravating effects of dietary magnesium deficiency on cartilage damage in an injury-induced murine OA model and to determine the underlying mechanism.

Methods

Twelve-week-old C57BL/6J mice subject to injury-induced OA modeling were randomized into different diet groups in which the mice were fed a diet with daily recommended magnesium content (500 mg/kg) or diets with low magnesium content (100 or 300 mg/kg). Articular cartilage damage was evaluated using the OARSI score. To determine molecular mechanisms in vitro, mouse chondrocytes were treated with media of low magnesium conditions at 0.1 and 0.4 mM, compared with normal magnesium condition at 0.7 mM as control. Anabolic and catabolic factors, autophagy markers, β-catenin, Wnt ligands, and a magnesium channel transient receptor potential cation channel subfamily member 7 (TRPM7) were analyzed by quantitative real-time PCR and immunoblotting. Autolysosomes were detected by DALGreen staining via fluorescence microscopy and autophagosomes were evaluated by transmission electron microscopy. Autophagy markers, β-catenin, and TRPM7 were assessed in vivo in the mouse cartilage, comparing between dietary magnesium deficiency and normal diet, by immunohistochemistry.

Results

Dietary magnesium deficiency aggravated injury-induced cartilage damage, indicated by significant higher OARSI scores. Autophagy markers LC3-II and Beclin-1 were decreased both in low magnesium diet-fed mice and low magnesium-treated chondrocytes. The number of autolysosomes and autophagosomes was also reduced under low magnesium conditions. Moreover, magnesium deficiency induced decreased anabolic and increased catabolic effect of chondrocytes which could be restored by autophagy activator rapamycin. In addition, reduced autophagy under low magnesium conditions is mediated by activated Wnt/β-catenin signaling. The expression of TRPM7 also decreased in low magnesium diet-fed mice, indicating that downstream changes could be regulated through this channel.

Conclusions

Dietary magnesium deficiency contributes to OA development, which is mediated by reduced autophagy through Wnt/β-catenin signaling activation. These findings indicated potential benefits of adequate dietary magnesium for OA patients or those individuals at high risk of OA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02848-0.

Quercetin mediates TSC2-RHEB-mTOR pathway to regulate chondrocytes autophagy in knee osteoarthritis

OBJECTIVE

This study aimed to explore the specific molecular mechanism of the therapeutic effect of quercetin in knee osteoarthritis (KOA).

METHODS

The KOA rat model was constructed by excising the medial meniscus and transecting the anterior meniscus. Joint injuries in rats were determined by Hematoxylin-Eosin (H&E) and Safranin O staining. The severity of KOA was then assessed according to the Osteoarthritis Research Society International (OARSI). The expressions of TSC2 and LC2B in joint tissue were measured by immunohistochemistry. Besides, chondrocytes treated with 10 ng/ml IL-1β were used to construct a chondrocyte arthritis model, while those treated with 4 or 8 μM quercetin were served as treatment groups. MTT, flow cytometry and toluidine blue staining were used to detect cell viability, apoptosis and mucopolysaccharide synthesis, respectively. qRT-PCR or Western blot was performed to determine the expressions of MMP-13, collagen II, Aggrecan, TSC2, RHEB, mTOR, p-mTOR, ULK1, p-ULK1, LC3B-I, LC3B-II and P62 in chondrocytes.

RESULTS

Quercetin alleviated the joint injury and suppressed the increase in MMP-13 expression and the decreases in collagen II and Aggrecan expressions in KOA rats. In addition, quercetin suppressed RHEB, p-mTOR, p-ULK1 and P62 expressions but promoted TSC2 and LC3BII expressions in KOA rats. Furthermore, quercetin could relieve the decrease of cell viability and the increase of apoptosis that induced by IL-1β, and promote the synthesis of IL-1β-inhibited mucopolysaccharide in chondrocytes. Nevertheless, siTSC2 partially offset the therapeutic effects of quercetin in chondrocytes.

CONCLUSION

Quercetin alleviated KOA by mediating the TSC2-RHBE-mTOR signaling pathway.

Noncoding RNAs in the Glycolysis of Ovarian Cancer

Energy metabolism reprogramming is the characteristic feature of tumors. The tumorigenesis, metastasis, and drug resistance of ovarian cancer (OC) is dependent on energy metabolism. Even under adequate oxygen conditions, OC cells tend to convert glucose to lactate, and glycolysis can rapidly produce ATP to meet their metabolic energy needs. Non-coding RNAs (ncRNAs) interact directly with DNA, RNA, and proteins to function as an essential regulatory in gene expression and tumor pathology. Studies have shown that ncRNAs regulate the process of glycolysis by interacting with the predominant glycolysis enzyme and cellular signaling pathway, participating in tumorigenesis and progression. This review summarizes the mechanism of ncRNAs regulation in glycolysis in OC and investigates potential therapeutic targets.

Effects of Mg-Nd-Gd-Sr alloy on bone marrow mesenchymal stem cell function derived from SD rats

Introduction

The aim of this study was to determine the effect of a new type of Mg-3Nd-1Gd-0.3Sr-0.2Zn-0.4Zr (abbreviated to Mg-Nd-Gd-Sr) alloy on bone marrow mesenchymal stem cell (BMSCs) function derived from SD rats.

Methods

BMSCs were first isolated and cultured in vitro using the whole bone marrow adherence method, and identified by BMSC surface biomarkers and osteogenic induction. The in vitro biological safety of the Mg-Nd-Gd-Sr alloy was studied by cytotoxicity and apoptosis experiments, and the in vitro biological functions were studied by cell adhesion and cell proliferation experiments.

Results

The results showed that high-purity BMSCs were isolated using the whole bone marrow adherence method. Flow cytometry showed high expression of CD44 and CD90, and low expression of CD31 and CD45 in the BMSCs. Osteogenic induction showed that the BMSCs differentiated into osteoblasts, and mineralized nodules were observed. The cytotoxicity of the Mg-Nd-Gd-Sr alloy to SD rat BMSCs was 0–1 grade, suggesting that the Mg-Nd-Gd-Sr alloy had no significant cytotoxic effect on SD rat BMSCs; compared with the control group, there was no significant cell apoptosis in any of the experimental groups ( p > 0.05). Cell adhesion experiments showed that the number of adherent cells increased with the duration of culture with the exception of the 100% concentration group; compared with the control group, the 75% concentration group had the highest number of adherent cells at the 1st, 3rd, 5th, and 7th hours ( p < 0.05). Cell proliferation experiments showed that the number of cells in all experiment groups was higher than the control group ( p < 0.05) on the 1st, 3rd, 5th, and 7th days, with the highest number of cells in the 75% concentration group ( p < 0.05).

Conclusion

Our data indicate that the extracts of new type of Mg-Nd-Gd-Sr alloy has no apparent cytotoxicity to BMSCs, does not affect cell apoptosis, and has good biocompatibility. Different concentrations of Mg-Nd-Gd-Sr alloy extracts promoted the adhesion and proliferation of BMSCs. The alloy had good biological functions, and is thus a promising bone repair material.

Targeting ERK induced cell death and p53/ROS-dependent protective autophagy in colorectal cancer

In recent years, many studies have shown that autophagy plays a vital role in the resistance of tumor chemotherapy. However, the interaction between autophagy and cell death has not yet been clarified. In this study, a new specific ERK inhibitor CC90003 was found to suppress colorectal cancer growth by inducing cell death both in vitro and in vivo. Studies have confirmed that higher concentrations of ROS leads to autophagy or cell death. In this research, the role of CC90003-induced ROS was verified. But after inhibiting ROS by two kinds of ROS inhibitors NAC and SFN, the autophagy induced by CC90003 decreased, while cell death strengthened. In parallel, protective autophagy was also induced, while in a p53-dependent manner. After silencing p53 or using the p53 inhibitor PFTα, the autophagy induced by CC90003 was weakened and the rate of cell death increases. Therefore, we confirmed that CC90003 could induce autophagy by activating ROS/p53. Furthermore, in the xenograft mouse model, the effect was obtained remarkably in the combinational treatment group of CC90003 plus CQ, comparing with that of the single treatment groups. In a word, our results demonstrated that targeting ERK leads to cell death and p53/ROS-dependent protective autophagy simultaneously in colorectal cancer, which offers new potential targets for clinical therapy.

Long noncoding RNA CRART16 confers 5-FU resistance in colorectal cancer cells by sponging miR-193b-5p

Background

The emergence of chemoresistance to 5-fluorouracil (5-FU)-based chemotherapy is the main cause of treatment failure in advanced and metastatic colorectal cancer (CRC) patients. Long noncoding RNAs (lncRNAs) have been reported to be involved in 5-FU resistance. Previously, we first detected that lncRNA cetuximab resistance-associated RNA transcript 16 (CRART16) could contribute to cetuximab resistance by upregulating V-Erb-B2 erythroblastic leukemia viral oncogene homologue 3 (ERBB3) expression by sponging miR-371a-5p in CRC cells. The current study aimed to explore the role of CRART16 in acquired 5-FU resistance in CRC cells and its possible mechanism.

Methods

Quantitative real-time PCR (RT-qPCR) was used to measure the expression levels of CRART16 in a 5-FU-resistant CRC cell subline (SW620/5-FU) and the parent cell line. Lentivirus transduction was performed to establish SW620 and Caco-2 cells stably overexpressing CRART16. Cell Counting Kit-8 (CCK-8) assays and colony formation assays were applied to measure cell chemosensitivity to 5-FU. Flow cytometric and immunofluorescence staining were adopted to assess cell apoptosis induced by 5-FU. The dual-luciferase reporter assay was used to validate the direct interactions between CRART16 and miR-193b-5p and between miR-193b-5p and high-mobility group AT-hook-2 (HMGA2). The expression levels of HMGA2, apoptosis-associated proteins and p-ERK were examined by western blotting. The statistical differences within any two groups were used Student’s t test.

Results

CRART16 was upregulated in SW620/5-FU cells. Overexpression of CRART16 reduced the sensitivity of CRC cells to 5-FU by attenuating apoptosis. In addition, CRART16 promoted 5-FU resistance by suppressing the expression of miR-193b-5p. Furthermore, CRART16 modulated the expression of HMGA2 by inhibiting miR-193b-5p and activated the MAPK signaling pathway.

Conclusions

CRART16 confers 5-FU resistance in CRC cells through the CRART16/miR-193b-5p/HMGA2/MAPK pathway.

Long term usage of dexamethasone accelerating accelerates the initiation of osteoarthritis via enhancing chondrocyte apoptosis and the extracellular matrix calcification and apoptosis of chondrocytes

Systemic application of glucocorticoids is an essential anti-inflammatory and immune-modulating therapy for severe inflammatory or autoimmunity conditions. However, its long-term effects on articular cartilage of patients' health need to be further investigated. In this study, we studied the effects of dexamethasone (Dex) on the homeostasis of articular cartilage and the progress of destabilization of medial meniscus (DMM)-induced osteoarthritis (OA) in adult mice. Long-term administration of Dex aggravates the proteoglycan loss of articular cartilage and drastically accelerates cartilage degeneration under surgically induced OA conditions. In addition, Dex increases calcium content in calcified cartilage layer of mice and the samples from OA patients with a history of long-term Dex treatment. Moreover, long term usage of Dex results in decrease subchondral bone mass and bone density. Further studies showed that Dex leads to calcification of extracellular matrix of chondrocytes partially through activation of AKT, as well as promotes apoptosis of chondrocytes in calcified cartilage layer. Besides, Dex weakens the stress-response autophagy with the passage of time. Taken together, our data indicate that long-term application of Dex may predispose patients to OA and or even accelerate the OA disease progression development of OA patients.

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.

The application prospect of metal/metal oxide nanoparticles in the treatment of osteoarthritis

The current understanding of osteoarthritis is developing from a mechanical disease caused by cartilage wear to a complex biological response involving inflammation, oxidative stress and other aspects. Nanoparticles are widely used in drug delivery due to its good stability in vivo and cell uptake efficiency. In addition to the above advantages, metal/metal oxide NPs, such as cerium oxide and manganese dioxide, can also simulate the activity of antioxidant enzymes and catalyze the degradation of superoxide anions and hydrogen peroxide. Degrading of metal/metal oxide nanoparticles releases metal ions, which may slow down the progression of osteoarthritis by inhibiting inflammation, promoting cartilage repair and inhibiting cartilage ossification. In present review, we focused on recent research works concerning osteoarthritis treating with metal/metal oxide nanoparticles, and introduced some potential nanoparticles that may have therapeutic effects.

Transforming Growth Factor Beta 1 and p44/42 Expression in Cardinal Ligament Tissues of Patients with Pelvic Organ Prolapse

Background

Pelvic organ prolapse (POP) is a disease associated with collagen loss and decreased fibroblast proliferation. Transforming growth factor beta 1 (TGF-β1) controls collagen synthesis and degradation in pelvic connective tissue. Although the p44/42 MAPK pathway has been implicated in collagen production and extracellular matrix disorders, its expression in POP remains unknown. This study aimed to investigate TGF-β1 and p44/42 expression in cardinal ligament tissues in patients with POP.

Material/Methods

Cardinal ligament tissues were obtained from 30 patients with POP (POP group) and 30 patients with benign gynecological disorders who had undergone total hysterectomy (control group). The clinical characteristics of the 2 groups were summarized. Immunohistochemical staining and western blotting analysis were performed to measure the expression of TGF-β1, p44/42, phospho-p44/42, MMP9, TIMP1, caspase 3, collagen I, and collagen III in the cardinal ligament tissues.

Results

Patients with POP had significantly lower TGF-β1 and phospho-p44/42 levels than did control patients (P<0.05). The expression of TIMP1, collagen I, and collagen III was significantly lower, and the expression of MMP9 and caspase 3 was significantly higher in the POP group than in the control group (P<0.05). Moreover, the expression of phospho-p44/42 was positively correlated with the expression of TGF-β1, collagen I, and collagen III.

Conclusions

The expression levels of phospho-p44/42 and TGF-β1 were decreased in patients with POP and were positively correlated with collagen expression. Low levels of TGF-β1 and phospho-p44/42 expression in patients with POP may be associated with the occurrence of POP.

Magnesium Deficiency Alters Expression of Genes Critical for Muscle Magnesium Homeostasis and Physiology in Mice

Chronic Mg²⁺ deficiency is the underlying cause of a broad range of health dysfunctions. As 25% of body Mg²⁺ is located in the skeletal muscle, Mg²⁺ transport and homeostasis systems (MgTHs) in the muscle are critical for whole-body Mg²⁺ homeostasis. In the present study, we assessed whether Mg²⁺ deficiency alters muscle fiber characteristics and major pathways regulating muscle physiology. C57BL/6J mice received either a control, mildly, or severely Mg²⁺-deficient diet (0.1%; 0.01%; and 0.003% Mg²⁺ wt/wt, respectively) for 14 days. Mg²⁺ deficiency slightly decreased body weight gain and muscle Mg²⁺ concentrations but was not associated with detectable variations in gastrocnemius muscle weight, fiber morphometry, and capillarization. Nonetheless, muscles exhibited decreased expression of several MgTHs (MagT1, CNNM2, CNNM4, and TRPM6). Moreover, TaqMan low-density array (TLDA) analyses further revealed that, before the emergence of major muscle dysfunctions, even a mild Mg²⁺ deficiency was sufficient to alter the expression of genes critical for muscle physiology, including energy metabolism, muscle regeneration, proteostasis, mitochondrial dynamics, and excitation–contraction coupling.

PNO1 regulates autophagy and apoptosis of hepatocellular carcinoma via the MAPK signaling pathway

Some studies have reported that activated ribosomes are positively associated with malignant tumors, especially in hepatocellular carcinoma (HCC). The RNA-binding protein PNO1 is a critical ribosome rarely reported in human tumors. This study aimed to explore the molecular mechanisms of PNO1 in HCC. Using 150 formalin-fixed and paraffin-embedded samples and 8 fresh samples, we found high PNO1 expression in HCC tumor tissues through Western blotting and RT-PCR. Moreover, the higher PNO1 expression was associated with poor HCC prognosis patients. In vitro and in vivo experiments indicated that PNO1 overexpression promoted the proliferation and depressed the apoptosis of HCC cells. High PNO1 expression also increased the autophagy of HCC cells. The molecular mechanisms underlying PNO1 were examined by RNA-seq analysis and a series of functional experiments. Results showed that PNO1 promoted HCC progression through the MAPK signaling pathway. Therefore, PNO1 was overexpressed in HCC, promoted autophagy, and inhibited the apoptosis of HCC cells through the MAPK signaling pathway.

Effect of infusion irrigation with different irrigating solutions on transient receptor potential vanilloid 5 and intra-articular inflammation in a post-traumatic osteoarthritis rabbit model

BACKGROUND

The incidence of post-traumatic osteoarthritis (PTOA) after anterior cruciate ligament reconstruction (ACLR) is high, but there is still a lack of intra-operative preventive measures. This study aimed to evaluate the effect of different irrigating solutions continuous irrigation on intra-articular inflammation and cartilage degeneration.

METHODS

66 New Zealand rabbits were randomly divided into normal (N) group, no treatment (NT) group, sodium chloride (NaCl) group, magnesium sulfate (MgSO4) group, and calcium chloride (CaCl2) group. The right knee joint of the experimental group was utilized to construct the model of PTOA, and the left side was utilized as the normal control group. At different time points postoperatively, the blood concentration of hemoglobin and Mg2 + , the synovial fluid concentration of IL-1 β, TNF-α, tartrate-resistant acid phosphatase-5b (TRAP-5b), and Type II Collagen, the gene expression of IL-1 β and MMP-3, and the protein expression of TRPV5 and CaM were detected. Pearson's linear correlation was employed to identify the possible relationship between the expression of TRAP-5b and the expression of IL-1β, IL-6, TNF-α, and Type II collagen. The hematoxylin and eosin staining (HE), Masson's trichrome staining, and Alcian blue staining were performed at postoperative 35 days. Osteoarthritis Scoring (OA score) comprised categories including Alcian blue staining, cartilage histology, the cellular density of cartilage, degree of cell disintegration, and formation of chondrocyte cluster were blindly scored by trained researchers at postoperative 35 days.

RESULTS

There was no statistical difference (P > 0.05) in the hemoglobin concentration between different groups. The concentration of serum Mg2+ in the MgSO4 group was higher than that of the other three groups (P < 0.05) on the same day of operation, then gradually decreased. The expression of IL-1 β, IL-6, and TRAP-5b in synovial fluid increased 5 days after the operation, decreased at 15 days, and then increased again with time in the NT group, NaCl group, and NT group and NaCl group. At 35 days after the operation, the expression of IL-1 β, IL-6, TRAP-5b, and type II collagen in the MgSO4 group were lower than that in the other three groups (except group N) (P < 0.05).The correlation analysis results showed that the TRAP-5b levels correlated positively with IL-1 β, IL-6, TNF-α, and type II collagen concentrations. The histological examination revealed that the surface smoothness of cartilage, the morphology of chondrocytes, the arrangement of collagen fibers, and the density of proteoglycan in the MgSO4 group were better than those in other experimental groups. At 35 days postoperatively, the gene expression of IL-1 β and MMP-3 and the protein expression of CaM and TRPV5 in synovium in the MgSO4 group was lower than that in the NaCl group and CaCl2 group.

CONCLUSION

Intra-operative irrigation with magnesium sulfate solution can inhibit the inflammatory factors and the expression of TRPV5, which can also reduce collagen loss and delay cartilage degeneration. Therefore, the use of magnesium sulfate in intra-operative irrigation may be an ideal choice to prevent PTOA.

Intra-articular magnesium to alleviate postoperative pain after arthroscopic knee surgery: a meta-analysis of randomized controlled trials

Objective

We aimed to evaluate the safety and efficacy of intra-articular (IA) magnesium (Mg) for postoperative pain relief after arthroscopic knee surgery.

Methods

We searched PubMed, Embase, Medline, Cochrane library, and Web of Science to identify randomized controlled trials that compared postoperative pain outcomes with or without IA Mg after knee arthroscopy. The primary outcomes were pain intensity at rest and with movement at different postoperative time points and cumulative opioid consumption within 24 h after surgery. Secondary outcomes included the time to first analgesic request and side effects.

Results

In total, 11 studies involving 677 participants met the eligibility criteria. Pain scores at rest and with movement 2, 4, 12, and 24 h after surgery were significantly lower, doses of supplementary opioid consumption were smaller, and the time to first analgesic requirement was longer in the IA Mg group compared with the control group. No significant difference was detected regarding adverse reactions between the groups.

Conclusions

Intra-articular magnesium is an effective and safe coadjuvant treatment for relieving postoperative pain intensity after arthroscopic knee surgery.

Protocol registration at PROSPERO: CRD42020156403.

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

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

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.

A Biodegradable Mg-Based Alloy Inhibited the Inflammatory Response of THP-1 Cell-Derived Macrophages Through the TRPM7-PI3K-AKT1 Signaling Axis

Mg-based alloys might be ideal biomaterials in clinical applications owing to favorable mechanical properties, biodegradability, biocompatibility, and especially their anti-inflammatory properties. However, the precise signaling mechanism underlying the inhibition of inflammation by Mg-based alloys has not been elucidated. Here, we investigated the effects of a Mg-2.1Nd-0.2Zn-0.5Zr alloy (denoted as JDBM) on lipopolysaccharide (LPS)-induced macrophages. THP-1 cell-derived macrophages were cultured on JDBM, Ti-6Al-4V alloy (Ti), 15% extract of JDBM, and 7.5 mM of MgCl2 for 1 h before the addition of LPS for an indicated time; the experiments included negative and positive controls. Our results showed JDBM, extract, and MgCl2 could decrease LPS-induced tumor necrosis factor (TNF) and interleukin (IL)-6 expression. However, there were no morphologic changes in macrophages on Ti or JDBM. Mechanically, extract and MgCl2 downregulated the expression of toll-like receptor (TLR)-4 and MYD88 compared with the positive control and inhibited LPS-induced nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways by inactivation of the phosphorylation of IKK-α/β, IKβ-α, P65, P38, and JNK. Additionally, the LPS-induced reactive oxygen species (ROS) expression was also decreased by extract and MgCl2. Interestingly, the expression of LPS-induced TNF and IL-6 could be recovered by knocking down TRPM7 of macrophages, in the presence of extract or MgCl2. Mechanically, the activities of AKT and AKT1 were increased by extract or MgCl2 with LPS and were blocked by a PI3K inhibitor, whereas siRNA TRPM7 inhibited only AKT1. Together, our results demonstrated the degradation products of Mg-based alloy, especially magnesium, and resolved inflammation by activation of the TRPM7-PI3K-AKT1 signaling pathway, which may be a potential advantage or target to promote biodegradable Mg-based alloy applications.