Challenges and strategies for in situ endothelialization and long-term lumen patency of vascular grafts

Vascular diseases are the most prevalent cause of ischemic necrosis of tissue and organ, which even result in dysfunction and death. Vascular regeneration or artificial vascular graft, as the conventional treatment modality, has received keen attentions. However, small-diameter (diameter < 4 mm) vascular grafts have a high risk of thrombosis and intimal hyperplasia (IH), which makes long-term lumen patency challengeable. Endothelial cells (ECs) form the inner endothelium layer, and are crucial for anti-coagulation and thrombogenesis. Thus, promoting in situ endothelialization in vascular graft remodeling takes top priority, which requires recruitment of endothelia progenitor cells (EPCs), migration, adhesion, proliferation and activation of EPCs and ECs. Chemotaxis aimed at ligands on EPC surface can be utilized for EPC homing, while nanofibrous structure, biocompatible surface and cell-capturing molecules on graft surface can be applied for cell adhesion. Moreover, cell orientation can be regulated by topography of scaffold, and cell bioactivity can be modulated by growth factors and therapeutic genes. Additionally, surface modification can also reduce thrombogenesis, and some drug release can inhibit IH. Considering the influence of macrophages on ECs and smooth muscle cells (SMCs), scaffolds loaded with drugs that can promote M2 polarization are alternative strategies. In conclusion, the advanced strategies for enhanced long-term lumen patency of vascular grafts are summarized in this review. Strategies for recruitment of EPCs, adhesion, proliferation and activation of EPCs and ECs, anti-thrombogenesis, anti-IH, and immunomodulation are discussed. Ideal vascular grafts with appropriate surface modification, loading and fabrication strategies are required in further studies.

Biodegradable JDBM coating stent has potential to be used in the treatment of benign biliary strictures

In our previous study, to find out the optimal alloy suitable for biliary surgery, magnesium alloy Jiao Da Bio-magnesium (denoted as JDBM) alloy, Zn-3Cu alloys, and their respective coating (MgF₂-PDLLA) products were produced for our research. We found that JDBM seems to be a potential material for clinical biliary stent application due to its uniform degradation and good compatibility. In order to apply the JDBM alloy to treat benign bile duct stricture, our group prepared the bare JDBM and its coating product into finished stents by mesh weaving carving technology and conducted the mechanical property tests, degradation tests and biocompatibility tests. During the mechanical property tests, we found the bare JDBM stent was more suitable than titanium alloy stent when applies to the bile duct, and the coating of the JDBM coating stent has no effect on its mechanical properties. Our in vitro and in vivo experiments revealed that the degradation rate of the JDBM coating stent is lower than that of the JDBM stent, and both stents were biosafe. Thus, there is promise for JDBM coating stents for the treatment of benign biliary strictures.

Effects of composition and hierarchical structures of calcium phosphate coating on the corrosion resistance and osteoblast compatibility of Mg alloys

Magnesium and its alloys have been recently used in biomedical applications such as orthopedic implants, whereas the weak corrosion resistance undermines their clinical efficacy. Herein, to address this critical challenge, the preparation of hierarchically structured hydroxyapatite-based coatings was proposed. Compact coatings were fabricated on a Mg alloy through a facile two-step method of chemical deposition of brushite precursor and subsequent hydrothermal conversion. A series of HA-based coatings were obtained with kinetic conversion process with formation mechanism revealed. The hydroxyapatite coating demonstrated the greatest corrosion resistance for Mg in electrochemical and long-term immersion tests, especially against pitting corrosion, attributable to its compact structure, alkaline degradation environment and self-induced growth capacity. The in vitro cytocompatibility and osteoinductivity were dictated. Additionally, anti-corrosion mechanisms were compared among different coating compositions and structures, along with their correlation with cellular response. Our study brings hints for a tailored surface design for resorbable biomedical device applications.

MicroRNA-596 is epigenetically inactivated and suppresses prostatic cancer cell growth and migration via regulating Wnt/β-catenin signaling

OBJECTIVES

Although studies have reported that miR-596 extensively participates in multiple cancer progression, the biological mechanisms and effects of miR-596 in prostatic cancer remain unclear. The literature is aimed to reveal the function and possible molecular mechanisms of miR-596 in prostatic cancer carcinogenesis.

MATERIALS AND METHODS

qRT-PCR was applied to examine miR-596 expression in prostatic cancer cell lines and samples, also methylation-specific PCR was used to detect the methylation status of the promoter CpG islands in prostatic cancer samples. Meanwhile, the tumor-related effects of miR-596 were detected via cell viability, clone formation assay, migration assay, flow cytometric and AO/EB assay. qRT-PCR and Western blots were applied to investigate the function of miR-596 on malignant behavior in prostatic cancer cells.

RESULTS

We found that miR-596 mRNA was decreased in prostatic cancer samples and cell lines. miR-596 mRNA level was also correlated to cancer stage, Gleason scores, while miR-596 promoter methylation was related to cancer tumor stage, Gleason score and preoperative PSA levels. miR-596 inhibited the cell growth and activity by causing cell apoptosis, and also suppressed the migration of prostatic cancer cells by revealing the epithelial-mesenchymal transition process. In addition, Western blot indicates that miR-596 overexpression deregulated Wnt/β-catenin signaling, by restraining phosphorylation levels of β-catenin and expression levels of downstream targets.

CONCLUSIONS

In summary, this research indicates that miR-596 overexpression could be potentially useful in the cell growth and migration of prostatic cancer and serves as a potential molecular marker in prostatic cancer.

RGS12 Represses Oral Cancer via the Phosphorylation and SUMOylation of PTEN

Oral squamous cell carcinoma (OSCC) is the most common head and neck cancer characterized by aggressive local invasion and metastasis. The pathogenesis of OSCC is mainly due to the accumulation of genetic alterations in epithelial cells, but the underlying mechanism for its development remains unclear. Here, we found that the expression level of regulator of G protein signaling 12 (RGS12) was significantly reduced in human OSCC. To understand the role and mechanism of RGS12 in OSCC, we generated a novel RGS12 global knockout (CMV^Cre/+; RGS12^fl/fl) mouse model by crossing RGS12^fl/fl mice with CMV-Cre transgenic mice and then further induced the mice to develop OSCC by using 4-nitroquinoline 1-oxide (4NQO). Deletion of RGS12 exhibited aggressive OSCC in the tongue compared with the control RGS12^fl/fl mice. Knockdown of RGS12 in OSCC cells significantly increased cell proliferation and migration. Mechanistically, we found that RGS12 associated with phosphatase and tension homolog (PTEN) via the PDZ domain to upregulate the phosphorylation and SUMOylation of PTEN and then correspondingly inactivated the AKT/mTOR signaling pathway. To test the potential therapeutic effect of RGS12 on OSCC, we overexpressed RGS12 in OSCC cells and found a significant inhibition of cancer cell proliferation and migration. Moreover, subcutaneous inoculation of RGS12-overexpressed OSCC cells in NOD scid mice showed a significant reduction in tumor formation. Our findings reveal that RGS12 is an essential tumor suppressor and highlights RGS12 as a potential therapeutic target and prognostic biomarker of OSCC.

WWP2 Promotes Odontoblastic Differentiation by Monoubiquitinating KLF5

WW domain-containing E3 Ub-protein ligase 2 (WWP2) belongs to the homologous to E6AP C-terminus (HECT) E3 ligase family. It has been explored to regulate osteogenic differentiation, chondrogenesis, and palatogenesis. Odontoblasts are terminally differentiated mesenchymal cells, which contribute to dentin formation in tooth development. However, it remained unknown whether WWP2 participated in odontoblast differentiation. In this study, WWP2 was found to be expressed in mouse dental papilla cells (mDPCs), odontoblasts, and odontoblastic-induced mDPCs by immunohistochemistry and Western blotting. Besides, WWP2 expression was decreased in the cytoplasm but increased in the nuclei of differentiation-induced mDPCs. When Wwp2 was knocked down, the elevated expression of odontoblast marker genes (Dmp1 and Dspp) in mDPCs induced by differentiation medium was suppressed. Meanwhile, a decrease of alkaline phosphatase (ALP) activity was observed by ALP staining, and reduced formation of mineralized matrix nodules was demonstrated by Alizarin Red S staining. Overexpression of WWP2 presented opposite results to knockdown experiments, suggesting that WWP2 promoted odontoblastic differentiation of mDPCs. Further investigation found that WWP2 was coexpressed and interacted with KLF5 in the nuclei, leading to ubiquitination of KLF5. The PPPSY (PY2) motif of KLF5 was essential for its physical binding with WWP2. Also, cysteine 838 (Cys838) of WWP2 was the active site for ubiquitination of KLF5, which did not lead to proteolysis of KLF5. Then, KLF5 was confirmed to be monoubiquitinated and transactivated by WWP2, which promoted the expression of KLF5 downstream genes Dmp1 and Dspp. Deletion of the PY2 motif of KLF5 or mutation of Cys838 of WWP2 reduced the upregulation of Dmp1 and Dspp. Besides, lysine (K) residues K31, K52, K83, and K265 of KLF5 were verified to be crucial to WWP2-mediated KLF5 transactivation. Taken together, WWP2 promoted odontoblastic differentiation by monoubiquitinating KLF5.

Nano-micrometer surface roughness gradients reveal topographical influences on differentiating responses of vascular cells on biodegradable magnesium

Distinctively directing endothelial cells (ECs) and smooth muscle cells (SMCs), potentially by surface topography cue, is of central importance for enhancing bioefficacy of vascular implants. For the first time, surface gradients with a broad range of nano-micrometer roughness are developed on Mg, a promising next-generation biodegradable metal, to carry out a systematic study on the response of ECs and SMCs. Cell adhesion, spreading, and proliferation are quantified along gradients by high-throughput imaging, illustrating drastic divergence between ECs and SMCs, especially in highly rough regions. The profound role of surface topography overcoming the biochemical cue of released Mg²⁺ is unraveled at different roughness ranges for ECs and SMCs. Further insights into the underlying regulatory mechanism are gained at subcellular and gene levels. Our work enables high-efficient exploration of optimized surface morphology for modulating favored cell selectivity of promoting ECs and suppressing SMCs, providing a potential strategy to achieve rapid endothelialization for Mg.

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Surface topography stimuli was engineered on Mg with varying roughness gradients.

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Ridge/valley network feature on Mg overperforms the influence of Mg²⁺.

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Optimized roughness facilitates proliferation of ECs while suppressing SMCs.

Biodegradable Zn-1.5Cu-1.5Ag alloy with anti-aging ability and strain hardening behavior for cardiovascular stents

Zn and its alloys are considered as a new class of biodegradable metals due to their moderate degradation rates and acceptable biocompatibility. However, inadequate mechanical properties limit their further applications, especially for cardiovascular stents. In this study, a novel biodegradable Zn-1.5Cu-1.5Ag (wt%) alloy with excellent mechanical properties was developed, and then its in vitro degradation and cytotoxicity were characterized. Microstructural characterization showed that hot extrusion produced a bimodal distribution of grain size and much finer secondary phase precipitates. The as-extruded alloy exhibited a satisfactory combination of strength and plasticity (yield strength: 162.0 ± 2.94 MPa, ultimate tensile strength: 220.3 ± 1.70 MPa and elongation: 44.13 ± 1.09%). After being aged at room temperature for 8 months, its mechanical properties increased about 10%, implying its good anti-aging ability. The strain hardening exponent (n) calculated from true stress-strain curve showed that this alloy has evident strain hardening. Immersion tests in c-SBF solution revealed that this alloy has a moderate corrosion rate (48.6 ± 4.14 μm/year) and slightly localized corrosion behavior. Electrochemical tests showed that a weak passive film formed on surface during degradation, which has a limited protective effect. The cytotoxicity tests exhibited that this alloy possesses acceptable in vitro biocompatibility, which is comparable to pure Zn. According to the results of mechanical properties, corrosion behavior and cytotoxicity, the Zn-1.5Cu-1.5Ag alloy can be regarded as a potential candidate for cardiovascular stent applications.

A Biomimetic Zinc Alloy Scaffold Coated with Brushite for Enhanced Cranial Bone Regeneration

Bone tissue engineering is considered as a promising pathway for bone regeneration and defect reconstruction, in which scaffolds play an important role. Zn alloy, which is a biodegradable metal material that has advantages of metallic and biodegradable characteristics, has its special features, especially the ideal degradation rate and acceptable biocompatibility, which make it worthy to be further investigated for medical applications. In this study, new biodegradable porous Zn alloy scaffolds with Ca-P coating were attempted to repair cranial bone defect, and in vitro and in vivo assays were conducted to evaluate its biocompatibility, osteo-inductivity, and osteo-conductivity. The results indicated that coated Zn alloy possessed good biocompatibility, with no cytotoxicity. It could also promote osteogenic differentiation and calcium deposition of rabbit BMSCs in vitro, and new bone formation around the scaffold in vivo. The biodegradable porous Zn alloy scaffold with Ca-P coating is considered to be promising in cranial bone defect repair.

CDC6 is up-regulated and a poor prognostic signature in glioblastoma multiforme

PURPOSE

Glioblastoma multiforme (GBM) represents the most common and the most malignant type of brain tumor. Cell division cycle 6 (CDC6), a gene associated with DNA replication initiation, has been proven to be associated with the prognosis of multiple tumors. In this study, we aim to explore the association between CDC6 expression and GBM carcinogenesis and prognosis.

METHODS

CDC6 expression in normal cells and GBM cells was explored by analyzing TCGA dataset, as well as by RT-PCR and western blot methods. Survival analysis was performed by the Kaplan-Meier method. Multivariate Cox-regression analysis was adopted to estimate the independence of CDC6 as a GBM prognostic factor.

RESULTS AND CONCLUSIONS

Elevated CDC6 levels in GBM tumor tissues compared with those in normal brain tissues were illustrated by analyzing the gene expression profiles from TCGA dataset, and confirmed by RT-PCR and western blot assays in GBM tumor and normal human astrocyte cell lines. Kaplan-Meier analysis indicated the negative influence of high CDC6 expression on GBM overall survival (OS) probability and days to progression (D2P) after initial treatment, but not on days to recurrence (D2R) after initial treatment. Multivariate Cox regression analysis showed CDC6 as an independent signature marker gene for GBM prognosis. In addition, the combination of CDC6 mRNA expression and CpG island methylator phenotype (CIMP) could sensitively predict 3-year OS and D2P. In conclusion, our study uncovered the role of CDC6 in GBM carcinogenesis and prognosis for the first time, which could shed new light on GBM diagnosis and treatment.

Targeting Local Osteogenic and Ancillary Cells by Mechanobiologically Optimized Magnesium Scaffolds for Orbital Bone Reconstruction in Canines

Large-sized orbital bone defects have serious consequences that destroy orbital integrity and result in maxillofacial deformities and vision loss. The treatment of orbital bone defects is currently palliative and not reparative, suggesting an urgent demand for biomaterials that regenerate orbital bones. In this study, via alloying, extrusion and surface modification, we developed mechanobiologically optimized magnesium (Mg) scaffolds (Ca-P-coated Mg-Zn-Gd scaffolds, referred to as Ca-P-Mg) for the orthotopic reconstruction of large-sized orbital bone defects. At 6 months after transplanting the scaffolds to a clinically relevant canine large animal model, large-sized defects were successfully bridged by an abundance of new bone with normal mechanical properties that corresponded to gradual degradation of the implants. The osteogenic and ancillary cells, including vascular endothelial cells and trigeminal neurons, played important roles in this process. The scaffolds robustly enhanced bone marrow mesenchymal stem cell (BMSC) osteogenic differentiation. In addition, the increased angiogenesis including increased ratio of the specific endothelial subtype CD31^hi endomucin^hi (CD31^hiEmcn^hi) endothelial cells can facilitate osteogenesis. Furthermore, the scaffolds trigger trigeminal neurons via transient receptor potential vanilloid subtype 1 (Trpv1) to produce the neuropeptide calcitonin gene-related peptide (CGRP), which promotes angiogenesis and osteogenesis. Overall, our investigations revealed the efficacy of Ca-P-Mg scaffolds in healing orbital bone defects and warrant further exploration of these scaffolds for clinical applications.

Ultra-long high quality catalyst-free WO3 nanowires for fabricating high-performance visible photodetectors

This work presents a study on the controlled growth of WO₃ nanowires via chemical vapor deposition without catalyst, and their potential applications in visible photodetectors. The influence of growth conditions on the morphology of WO₃ nanowires is studied in order to understand the growth mechanism of WO₃ nanowires, and ultra-long (60 [Formula: see text], the longest one ever reported) WO₃ nanowires with a spindle shape are achieved by optimizing the growth conditions. It was found that the length of WO₃ nanowires increases from 15 [Formula: see text] to 60 [Formula: see text] with increasing the argon carrier gas flow rate from 30 sccm to 90 sccm, and then saturates with further increasing the argon carrier gas flow rate. However, the length of WO₃ nanowires reduces from 60 [Formula: see text] to 19 [Formula: see text] with increasing the tube inner pressure from 2.5 Torr to 3.5 Torr. The photoconductor detectors based on WO₃ single nanowires present excellent device performance with a responsivity as high as 19 A W^-1 at a bias of 0.1 V, a detectivity as high as 1.06 × 10¹¹ Jones, and a response (rising and decay) time as short as 8 ms under the illumination of a 404 nm laser. These results indicate the great potential of WO₃ nanowires for applications in fabricating high performance visible photodetectors.

The bioeffects of degradable products derived from a biodegradable Mg-based alloy in macrophages via heterophagy

Biodegradable magnesium alloys are promising candidates for use in biomedical applications. However, degradable particles (DPs) derived from Mg-based alloys have been observed in tissue in proximity to sites of implantation, which might result in unexpected effects. Although previous in vitro studies have found that macrophages can take up DPs, little is known about the potential phagocytic pathway and the mechanism that processes DPs in cells. Additionally, it is necessary to estimate the potential bioeffects of DPs on macrophages. Thus, in this study, DPs were generated from a Mg-2.1Nd-0.2Zn-0.5Zr alloy (JDBM) by an electrochemical method, and then macrophages were incubated with the DPs to reveal the potential impact. The results showed that the cell viability of macrophages decreased in a concentration-dependent manner in the presence of DPs due to effects of an apoptotic pathway. However, the DPs were phagocytosed into the cytoplasm of macrophages and further degraded in phagolysosomes, which comprised lysosomes and phagosomes, by heterophagy instead of autophagy. Furthermore, several pro-inflammatory cytokines in macrophages were upregulated by DPs through the induction of reactive oxygen species (ROS) production. To the best of our knowledge, this is the first study to show that DPs derived from a Mg-based alloy are consistently degraded in phagolysosomes after phagocytosis by macrophages via heterophagy, which results in an inflammatory response owing to ROS overproduction. Thus, our research has increased the knowledge of the metabolism of biodegradable Mg metal, which will contribute to an understanding of the health effects of biodegradable magnesium metal implants used for tissue repair. STATEMENT OF SIGNIFICANCE: Biomedical degradable Mg-based alloys have great promise in applied medicine. Although previous studies have found that macrophages can uptake degradable particles (DPs) in vitro and observed in the sites of implantation in vivoin vivo, few studies have been carried out on the potential bioeffects relationship between DPs and macrophages. In this study, we analyzed the bioeffects of DPs derived from a Mg-based alloy on the macrophages. We illustrated that the DPs were size-dependently engulfed by macrophages via heterophagy and further degraded in the phagolysosome rather than autophagosome. Furthermore, DPs were able to induce a slight inflammatory response in macrophages by inducing ROS production. Thus, our research enhances the knowledge of the interaction between DPs of Mg-based alloy and cells, and offers a new perspective regarding the use of biodegradable alloys.

Degradation and osteogenic induction of a SrHPO4-coated Mg-Nd-Zn-Zr alloy intramedullary nail in a rat femoral shaft fracture model

Magnesium and Mg-based alloys are promising biomaterials for orthopedic implants because of their degradability, osteogenic effects, and biocompatibility. However, the drawbacks of these materials include high hydrogen gas production, unexpected corrosion resistance, and insufficient mechanical strength duration. Surface modification can protect these biomaterials and induce osteogenesis. In this work, a SrHPO₄ coating was developed for our patented biodegradable Mg-Nd-Zn-Zr alloy (abbr. JDBM) through a chemical deposition method. The coating was characterized by in vitro immersion, ion release, and cytotoxicity tests, which showed a slower corrosion behavior and excellent cell viability. RNA sequencing of MC3T3E1 cells treated with SrHPO₄-coated JDBM ion release test extract showed increased Tlr4, followed by the activation of the downstream PI3K/Akt signaling pathway, causing proliferation and growth of pre-osteoblasts. An intramedullary nail (IMN) was implanted in a femoral fracture rat model. Mechanical test, radiological and histological analysis suggested that SrHPO₄-coated JDBM has superior mechanical properties, induces more bone formation, and decreases the degradation rate compared with uncoated JDBM and the administration of TLR4 inhibitor attenuated the new bone formation for fracture healing. SrHPO₄ is a promising coating for JDBM implants, particularly for long-bone fractures.

Mdm2 Promotes Odontoblast-like Differentiation by Ubiquitinating Dlx3 and p53

Dentin is an important structural component of the tooth. Odontoblast differentiation is an essential biological process that guarantees normal dentin formation, which is precisely regulated by various proteins. Murine double minute 2 (Mdm2) is an E3 ubiquitin ligase, and it plays a pivotal role in the differentiation of different cell types, such as osteoblasts and myoblasts. However, whether Mdm2 plays a role in odontoblast differentiation remains unknown. Here, we investigated the spatiotemporal expression of Mdm2 by immunostaining and found that Mdm2 was highly expressed in the odontoblasts and slightly in the dental papilla cells of mouse incisors and molars. Gene knockdown and overexpression experiments verified that Mdm2 promoted the odontoblast-like differentiation of mouse dental papilla cells (mDPCs). Intranuclear colocalization and physical interaction between Mdm2 and distal-less 3 (Dlx3), a transcription factor important for odontoblast differentiation, was found during the odontoblast-like differentiation of mDPCs by double immunofluorescence and immunoprecipitation. Mdm2 was proved to monoubiquitinate Dlx3, which enhanced the expression of Dlx3 target gene Dspp. In addition, p53, the canonical substrate of Mdm2, was validated to be also ubiquitinated but degraded by Mdm2 during the odontoblast-like differentiation of mDPCs. Gene knockdown experiments confirmed that p53 inhibited the odontoblast-like differentiation of mDPCs. p53 and Mdm2 double knockdown partially rescued the reduced odontoblast-like differentiation by knockdown of Mdm2 alone. Taken together, our study revealed that Mdm2 promoted the odontoblast-like differentiation of mDPCs by ubiquitinating both Dlx3 and p53. On one hand, the monoubiquitination of Dlx3 by Mdm2 led to upregulation of Dspp, which is a marker of the odontoblast differentiation. On the other hand, ubiquitination of p53 by Mdm2 resulted in its degradation, which eliminated the inhibitory effect of p53 on the odontoblast-like differentiation of mDPCs.

Comparative assessment of the biocompatibility and degradation behavior of Zn-3Cu and JDBM alloys used for biliary surgery

This study was designed to investigate the biocompatibility and the degradation behavior of a Zn-3Cu alloy, a Zn-3Cu coating alloy, a Mg-Nd-Zn-Zr (denoted as JDBM) alloy and a JDBM coating alloy to choose the optimal alloy for common bile duct (CBD) surgery. In the in vitro degradation experiments, we observed the surface morphology of the samples and determined the elements of the corrosion products. In the in vitro cytotoxicity experiments, the cell morphology and cytotoxicity were observed and tested. In the in vivo experiments, in addition to analyzing the samples, we also analyzed the variations in serum magnesium, serum creatinine (CREA), blood urea nitrogen (BUN), total bilirubin (TB) and glutamic pyruvic transaminase (GPT). Moreover, important tissue samples from the CBD, liver, kidney and spleen were taken for histological evaluation. The in vitro degradation experiments revealed that the surface corrosion of the JDBM and JDBM coating alloys were more obvious than that of Zn-3Cu and Zn-3Cu coating alloys, and the degradation rate of the JDBM coating alloy was the slowest. The in vitro cytotoxicity assessment showed that the JDBM alloy and JDBM coating alloy extracts were biologically safe for L-929 cells, while the Zn-3Cu alloy and Zn-3Cu coating alloy extracts were harmful to L-929 cells. In the in vivo experiments, neither the JDBM alloy nor the JDBM coating alloy affected the function or morphology of the bile duct, liver, kidney or spleen. Similar to the in vitro degradation behavior, the surface corrosion of the JDBM alloy was more significant than that of the JDBM coating alloy. Our data suggested that the JDBM coating alloy is a safe, biodegradable material for CBD surgery.

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.

In vivo and in vitro evaluation of a biodegradable magnesium vascular stent designed by shape optimization strategy

The performance of biodegradable magnesium alloy stents (BMgS) requires special attention to non-uniform residual stress distribution and stress concentration, which can accelerate localized degradation after implantation. We now report on a novel concept in stent shape optimization using a finite element method (FEM) toolkit. A Mg-Nd-Zn-Zr alloy with uniform degradation behavior served as the basis of our BMgS. Comprehensive in vitro evaluations drove stent optimization, based on observed crimping and balloon inflation performance, measurement of radial strength, and stress condition validation via microarea-XRD. Moreover, a Rapamycin-eluting polymer coating was sprayed on the prototypical BMgS to improve the corrosion resistance and release anti-hyperplasia drugs. In vivo evaluation of the optimized coated BMgS was conducted in the iliac artery of New Zealand white rabbit with quantitative coronary angiography (QCA), optical coherence tomography (OCT) and micro-CT observation at 1, 3, 5-month follow-ups. Neither thrombus or early restenosis was observed, and the coated BMgS supported the vessel effectively prior to degradation and allowed for arterial healing thereafter. The proposed shape optimization framework based on FEM provides an novel concept in stent design and in-depth understanding of how deformation history affects the biomechanical performance of BMgS. Computational analysis tools can indeed promote the development of biodegradable magnesium stents.

Degradation Products of Polydopamine Restrained Inflammatory Response of LPS-Stimulated Macrophages Through Mediation TLR-4-MYD88 Dependent Signaling Pathways by Antioxidant

Polydopamine (PDA) has a promising application as coating of biomaterials due to its favorable degradability and bioadaptability. However, its bioactivity, such as anti-inflammatory capacity, was still little known. Herein, we investigated whether degradable products of PDA could affect inflammatory response in lipopolysaccharide (LPS)-stimulated human THP-1-derived macrophages. The supernatants containing degradation products of PDA, annotated as PDA extracts, were collected after PDA being immersed in cell culture medium for 3 days. Wherein, the composition of the degradation products was analyzed by HPLC assay. Collected PDA extracts were diluted into 100%, 50%, and 25% of original concentration, respectively, to evaluate their anti-inflammatory ability on LPS-induced macrophages from the expression levels of pro-inflammatory cytokines to associated molecular mechanism. Our results showed that the PDA extracts were mainly composed of dopamine, quinine, and PDA segments. Furthermore, macrophages showed no cytotoxicity after PDA extract treatment with or without LPS, while the release levels of TNF-α and IL-6 by LPS-induced macrophages were decreased in dose-dependent by PDA extract treatment. Additionally, TLR-4 and MYD88 expression in protein and RNA level were downregulated by PDA extracts in LPS-induced macrophages. Similarly, PDA extracts effectively inhibited LPS-induced NF-κB trans-locating into nuclear by inactivation of the phosphorylation of IKK-α/β and IKβ-α. Of note, the production of LPS-induced ROS was reduced by PDA extracts in macrophages, while HO-1 expression, a critical protein of antioxidant signaling pathway, was increased. Based on these results, we proposed a potential mechanism by which degradation products of PDA suppressed inflammation of macrophages via downregulation TLR-4-MYD88-NFκB pathway and simultaneous activation HO-1 pathway, which might be a possible therapeutic target.

A pilot study of a novel biodegradable magnesium alloy airway stent in a rabbit model

OBJECTIVE

To preliminarily investigate the feasibility of bioabsorption tracheal stenting for the therapeutic application of congenital tracheal stenosis (CTS).

STUDY DESIGN

Experimental research.

SETTING

Shanghai Children Medical Center, National Children's Medical Center.

SUBJECTS AND METHODS

Five kinds of magnesium alloys with different compositions were studied in this paper, a patented Mg-Nd-Zn-Zr alloy series namely JDBM (JiaoDa BioMg) and four Mg-Ca-Zn alloys. The cytotoxicity of alloys was evaluated by the MTS ([3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay in rabbit tracheal epithelial cells. Specific magnesium alloys had been immersed in the cell culture medium for 24 h. The tracheal stents that were made of magnesium alloy were implanted into the trachea of New Zealand rabbits and the ablation of the stent was monitored by fiber bronchoscopy. The routine blood examination was conducted prior to and following the stent placement. The rabbits were euthanized following 2-3 months of stenting. H&E staining of the main organs was conducted and the induction of apoptosis of the tracheal tissues was monitored.

RESULTS

The cytotoxicity of the JDBM magnesium alloy was mild and lower than the remaining 4 alloys. The stents were placed successfully in five animals. The tracheal stents were successfully placed and gradually biodegradated as monitored by fiber bronchoscopy; no significant systemic inflammatory response was noted. No significant differences in the liver and/or kidney function prior to and following stent placement were noted. H&E staining indicated the absence of pathological changes in the trachea, liver, heart and/or kidney tissues. The apoptotic assay indicated that the apoptosis ratio of the tracheal tissues was comparable between rabbits with and without tracheal stenting.

CONCLUSION

The results suggested the feasibility of bioabsorption stents made of biodegradable magnesium alloys using in patients with tracheal stenosis, especially in infants.