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Background: Unlike the adult meniscus, the fetal meniscus possesses robust healing capacity. The dense and stiff matrix of the adult meniscus provides a biophysical barrier for cell migration, which is not present in the fetal meniscus. Inspired by developmental characteristics, modifying the matrix of the adult meniscus into a fetal-like, loose and soft microenvironment holds opportunity to facilitate repair, especially in the avascular zone. Hypothesis: Modifying the dense and stiff matrix of the adult meniscus into a fetal-like, loose and soft microenvironment could enhance cell migration to the tear interface and subsequent robust healing capacity. Study Design: Controlled laboratory study. Methods: Fresh porcine menisci were treated with hyaluronidase or collagenase. The density and arrangement of collagen fibers were assessed. The degradation of proteoglycans and collagen was evaluated histologically. Cell migration within the meniscus or the infiltration of exogenous cells into the meniscus was examined. Dendritic silica nanoparticles with relatively large pores were used to encapsulate hyaluronidase for rapid release. Mesoporous silica nanoparticles with relatively small pores were used to encapsulate transforming growth factor–beta 3 (TGF-β3) for slow release. A total of 24 mature male rabbits were included. A longitudinal vertical tear (0.5 cm in length) was prepared in the avascular zone of the medial meniscus. The tear was repaired with suture, repaired with suture in addition to blank silica nanoparticles, or repaired with suture in addition to silica nanoparticles releasing hyaluronidase and TGF-β3. Animals were sacrificed at 12 months postoperatively. Meniscal repair was evaluated macroscopically and histologically. Results: The gaps between collagen bundles increased after hyaluronidase treatment, while collagenase treatment resulted in collagen disruption. Proteoglycans degraded after hyaluronidase treatment in a dose-dependent manner, but collagen integrity was maintained. Hyaluronidase treatment enhanced the migration and infiltration of cells within meniscal tissue. Last, the application of fibrin gel and the delivery system of silica nanoparticles encapsulating hyaluronidase and TGF-β3 enhanced meniscal repair responses in an orthotopic longitudinal vertical tear model. Conclusion: The gradient release of hyaluronidase and TGF-β3 removed biophysical barriers for cell migration, creating a fetal-like, loose and soft microenvironment, and enhanced the fibrochondrogenic phenotype of reparative cells, facilitating the synthesis of matrix and tissue integration. Clinical Relevance: Modifying the adult matrix into a fetal-like, loose and soft microenvironment via the local gradient release of hyaluronidase and TGF-β3 enhanced the healing capacity of the meniscus. [ABSTRACT FROM AUTHOR]

Coronary perforation (CP) is a rare complication of percutaneous coronary intervention (PCI) and can lead to pericardial tamponade. Prolonged balloon inflation is a reasonable treatment for CP, but there is no standard recommendation on the preferable choice between the balloon site for prolonged balloon inflation (ie, proximal and in situ of the perforation). We present a rare case of successful prolonged balloon inflation at the proximal site of the CP after the failure of balloon inflation at the site of perforation. The patient developed CP during balloon inflation post-stent, rapidly progressing to cardiac tamponade. In situ prolonged balloon inflation (3 times) failed to close the CP, but proximal inflation could manage the CP. The take-home message from this case is that balloon expansion at the proximal site could be better than in situ of perforation in patients with CP after PCI. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) function as gene expression switches, and participate in diverse pathophysiological processes of spinal cord injury (SCI). Olfactory ensheathing cells (OECs) can alleviate pathological injury and facilitate functional recovery after SCI. However, the mechanisms by which OECs restore function are not well understood. This study aims to determine whether silencing miR-199a-5p would enhance the beneficial effects of the OECs. In this study, we measured miR-199a-5p levels in rat spinal cords with and without injury, with and without OEC transplants. Then, we transfected OECs with the sh-miR-199a-5p lentiviral vector to reduce miR-199a-5p expression and determined the effects of these OECs in SCI rats by Basso–Beattie–Bresnahan (BBB) locomotor scores, diffusion tensor imaging (DTI), and histological methods. We used western blotting to measure protein levels of Slit1, Robo2, and srGAP2. Finally, we used the dual-luciferase reporter assay to assess the relationship between miR-199-5p and Slit1, Robo2, and srGAP2 expression. We found that SCI significantly increased miR-199a-5p levels (P < 0.05), and OEC transplants significantly reduced miR-199a-5p expression (P < 0.05). Knockdown of miR-199a-5p in OECs had a better therapeutic effect on SCI rats, indicated by higher BBB scores and fractional anisotropy values on DTI, as well as histological findings. Reducing miR-199a-5p levels in transplanted OECs markedly increased spinal cord protein levels of Slit1, Robo2, and srGAP2. Our results demonstrated that transplantation of sh-miR-199a-5p-modified OECs promoted functional recovery in SCI rats, suggesting that miR-199a-5p knockdown was more beneficial to the therapeutic effects of OEC transplants. These findings provided new insights into miRNAs-mediated therapeutic mechanisms of OECs, which helps us to develop therapeutic strategies based on miRNAs and optimize cell therapy for SCI. [ABSTRACT FROM AUTHOR]

Fibre-reinforced polymer (FRP) composites with thermosetting resin matrices are widely used in civil engineering (e.g. pultruded FRP plates and bars), and their thermal ageing behaviour is a concern when they are subjected to elevated temperatures (e.g. FRP chimney). In the present article, the effects of thermal ageing at 200°C and 250°C in air for up to 1000 h on mechanical properties and mechanism of the benzoxazine (Boz), bisphenol A dicyanate cyanate ester (BADCy), and 4,4′-bismaleimidodiphenyl methane (BMI) have been investigated. The effect of time in thermal ageing on structural and mechanical properties of the Boz/BMI/BADCy resin was deeply studied. The moisture absorption increases linearly with the square root of ageing time and it follows Fick's second law. There are two main categories of reactions in thermal ageing: the first one is the post-curing process, which leads to a larger crosslinking density and a reduced interior stress; while the other is the formation of microcracks and thermal oxidation at the surface of the Boz/BMI/BADCy resin. The combination of the above factors leads to an increase–decrease variation in the mechanical properties. This work is believed to benefit the wide and safe application of a certain Boz/BMI/BADCy resin system in engineering application. [ABSTRACT FROM AUTHOR]

The polymerization mechanism of allyl-functional benzoxazine (Bz) monomers is reported in this article. Following the traditional route of Bz synthesis, a series of monofunctional Bz monomers were synthesized via allylamine and amine condensation reaction with 2,2′-diallyl bisphenol-A and paraformaldehyde. Resulting chemical structures of the synthesized monomers were confirmed by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance analyses. The polymerization behavior of the prepared allyl-functional monomers was studied using differential scanning calorimetry and FTIR. Three reactions were observed in the curing process: polymerization reaction of N-allyl groups in the oxazine ring, ring-opening polymerization of Bz, and polymerization reaction of allyl groups in benzene. Compared to a typical polybenzoxazine (PBz), higher cross-linking density in PBz-allyl-2 leads to a higher glass transition temperature and 5% weight loss temperature, which indicates improved thermal stability in PBz-allyl-2 as well as superior thermal conductivity compared to 2,2′-bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl)propane. Data on dielectric properties also show that PBz-allyl-2 outperforms typical PBzs. This work focuses on the manipulation of Bz monomer structures to alter their ring-opening polymerization mechanism, as well as cross-linking, in order to derive a PBz with improved properties. [ABSTRACT FROM AUTHOR]

In this study, hyperbranched polyimides were prepared from 2,6-bis(4-aminophenyl)-4-(4-(4-aminophenoxy)phenyl)pyridine (BAAP) and commercial dianhydrides by strictly controlling the reaction conditions. Polyimides with phthalimide pendants were also prepared to study the influence mechanisms of terminating BAAP by phthalic anhydride (PA) on polyimides’ properties. Fourier transform infrared and proton nuclear magnetic resonance spectroscopies were utilized to observe the chemical structures of the hyperbranched polyimides. The influence of terminating BAAP by PA on polyimides’ properties was studied by comparing the two series of polyimides. All the polyimide samples held completely amorphous structures and possessed excellent solubility and thermal stability. Terminating BAAP by PA decreased the d-spacing values of the obtained polyimides and slightly weakened their solubility and thermal stability. [ABSTRACT FROM AUTHOR]

This study reports on the preparation and thermal decomposition kinetics of a polyimide (PI) with phthalimide pendant (PI-1) and an analogous hyperbranched PI (PI-2). PI-1 was synthesized from 2,6-bis(4-aminophenyl)-4-(4-(4-aminophenoxy) phenyl) pyridine (BAAP) and 4,4′-(hexa-fluoroisopropylidene) diphthalic anhydride using a simple method with BAAP terminated by phthalic anhydride. The morphology of the PI structures was examined using X-ray diffraction. The thermal decomposition processes of the PIs were then studied according to a two-stage method using thermogravimetric analysis. The results indicated that both PIs exhibited excellent thermal stability, with a decomposition pattern of 5% mass loss beyond 508°C and 10% beyond 529°C. The two PIs exhibited similar levels of thermal stability in the first decomposition stage, but PI-1 exhibited higher stability in the second stage. The results indicate that PIs into which phthalimide pendants have been introduced retain their thermal stability in the first stage of decomposition and demonstrate enhanced thermal stability in the second stage. [ABSTRACT FROM AUTHOR]