In vivo study of microarc oxidation coated biodegradable magnesium plate to heal bone fracture defect of 3mm width.

Microarc oxidation (MAO) coated magnesium (Mg) with improved corrosion resistance appeal increasing interests as a revolutionary biodegradable metal for fractured bone fixing implants application. However, the in vivo corrosion degradation of the implants and bone healing response are not well understood, which is highly required in clinic. In the present work, 10µm and 20µm thick biocompatible MAO coatings mainly composed of MgO, Mg2SiO4, CaSiO3 and Mg3(PO4)2 phases were fabricated on AZ31 magnesium alloy. The electrochemical tests indicated an improved corrosion resistance of magnesium by the MAO coatings. The 10µm and 20µm coated and uncoated magnesium plates were separately implanted into the radius bone fracture site of adult New Zealand white rabbits using a 3mm width bone fracture defect model to investigate the magnesium implants degradation and uninhibited bone healing. Taking advantage of the good biocompatibility of the MAO coatings, no adverse effects were detected through the blood test and histological examination. The implantation groups of coated and uncoated magnesium plates were both observed the promoting effect of bone fracture healing compared with the simple fracture group without implant. The releasing Mg2+ by the degradation of implants into the fracture site improved the bone fracture healing, which is attributed to the magnesium promoting CGRP-mediated osteogenic differentiation. Mg degradation and bone fracture healing promoting must be tailored by microarc oxidation coating with different thickness for potential clinic application.

ErbB4 signaling in the prelimbic cortex regulates fear expression.

Many psychiatric diseases such as post-traumatic stress disorder (PTSD) are characterized by abnormal processing of emotional stimuli particularly fear. The medial prefrontal cortex (mPFC) is critically involved in fear expression. However, the molecular mechanisms underlying this process are largely unknown. Neuregulin-1 (NRG1) reportedly regulates pyramidal neuronal activity via ErbB4 receptors, which are abundant in parvalbumin (PV)-expressing interneurons in the PFC. In this study, we aimed to determine how NRG1/ErbB4 signaling in the mPFC modulates fear expression and found that tone-cued fear conditioning increased NRG1 expression in the mPFC. Tone-cued fear conditioning was inhibited following neutralization of endogenous NRG1 and specific inhibition or genetic ablation of ErbB4 in the prelimbic (PL) cortex but not in the infralimbic cortex. Furthermore, ErbB4 deletion specifically in PV neurons impaired tone-cued fear conditioning. Notably, overexpression of ErbB4 in the PL cortex is sufficient to reverse impaired fear conditioning in PV-Cre;ErbB4-/- mice. Together, these findings identify a previously unknown signaling pathway in the PL cortex that regulates fear expression. As both NRG1 and ErbB4 are risk genes for schizophrenia, our study may shed new light on the pathophysiology of this disorder and help to improve treatments for psychiatric disorders such as PTSD.

Celecoxib inhibits ß-catenin-dependent survival of the human osteosarcoma MG-63 cell line.

Cyclo-oxygenase (COX)-2 inhibitors may exert antitumour effects through COX-2-independent mechanisms. This study investigated the effects of the COX-2 inhibitor celecoxib on the viability of the human osteosarcoma MG-63 cell line and its ß-catenin signalling pathway. Cell viability and apoptosis were examined in celecoxib-treated cells or after ß-catenin knockdown in vitro. Analyses were performed to detect glycogen synthase kinase (GSK)-3ß, phosphorylated GSK-3ß, ß-catenin, c-Myc and cyclin D1 proteins, and mRNA levels of ß-catenin, c-Myc and CCND1 (encoding cyclin D1). ß-Catenin was shown to be required for MG63 cell survival and celecoxib exerted an inhibitory effect on the viability of cultured MG-63 cells in a time- and dose-dependent manner. ß-Catenin protein decreased in the cytosol and nucleus following celecoxib treatment (from 6 h after initiation of treatment onwards; lowest protein levels were reached at > 72 h). Significant reductions in ß-catenin, c-Myc and CCND1 mRNA were observed. Celecoxib inhibited MG-63 cell viability, possibly by activating GSK-3ß and inhibiting ß-catenin-dependent gene transcription, suggesting a role for celecoxib in osteosarcoma treatment.

A single base mutation in type I procollagen (COL1A1) that converts glycine alpha 1-541 to aspartate in a lethal variant of osteogenesis imperfecta: detection of the mutation with a carbodiimide reaction of DNA heteroduplexes and direct sequencing of products of the PCR.

Skin fibroblasts from a proband with a lethal variant of osteogenesis imperfecta synthesized both apparently normal type I procollagen and a type I procollagen that had slow electrophoretic mobility because of posttranslational overmodifications. The thermal unfolding of the collagen molecules as assayed by protease digestion was about 2 degrees C lower than normal. It is surprising, however, that collagenase A and B fragments showed an essentially normal melting profile. Assay of cDNA heteroduplexes with a new technique involving carbodiimide modification indicated a mutation at about the codon for amino acid 550 of the alpha 1(I) chain. Subsequent amplification of the cDNA by the PCR and nucleotide sequencing revealed a single-base mutation that substituted an aspartate codon for glycine at position alpha 1-541 in the COL1A1 gene. The results here confirm previous indications that the effects of glycine substitutions in type I procollagen are highly position specific. They also demonstrate that a recently described technique for detecting single-base differences by carbodiimide modification of DNA heteroduplexes can be effectively employed to locate mutations in large genes.