Regulation of embryonic and adult neurogenesis by Ars2.

Neural development is controlled at multiple levels to orchestrate appropriate choices of cell fate and differentiation. Although more attention has been paid to the roles of neural-restricted factors, broadly expressed factors can have compelling impacts on tissue-specific development. Here, we describe in vivo conditional knockout analyses of murine Ars2, which has mostly been studied as a general RNA-processing factor in yeast and cultured cells. Ars2 protein expression is regulated during neural lineage progression, and is required for embryonic neural stem cell (NSC) proliferation. In addition, Ars2 null NSCs can still transition into post-mitotic neurons, but fail to undergo terminal differentiation. Similarly, adult-specific deletion of Ars2 compromises hippocampal neurogenesis and results in specific behavioral defects. To broaden evidence for Ars2 as a chromatin regulator in neural development, we generated Ars2 ChIP-seq data. Notably, Ars2 preferentially occupies DNA enhancers in NSCs, where it colocalizes broadly with NSC regulator SOX2. Ars2 association with chromatin is markedly reduced following NSC differentiation. Altogether, Ars2 is an essential neural regulator that interacts dynamically with DNA and controls neural lineage development.

Luteolin induces mitochondrial apoptosis in HT29 cells by inhibiting the Nrf2/ARE signaling pathway.

The aim of the current study was to investigate luteolin-induced apoptosis and the molecular mechanisms underlying it in HT29 cells. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to assess the cytotoxicity of luteolin on HT29 cells, and a dichloro-dihydro-fluorescein diacetate assay was used to measure cellular levels of reactive oxygen species (ROS). The effects of luteolin on the mitochondrial membrane potential were also evaluated. Bax and Bcl-2 mRNA expression were determined using reverse transcription-quantitative PCR. Additionally, western blot analysis was performed to assess changes in cytochrome c and caspase-3 protein expression. Localization of nuclear factor erythroid 2-related factor 2 (Nrf2) in the nucleus was also assessed using immunofluorescence. Luteolin exhibited cytotoxicity on HT29 cells in a time- and concentration-dependent manner. Additionally, ROS production was indicated to be increased and ROS scavenging was decreased, which resulted in a significant increase in the levels of ROS in the cells. The mitochondrial membrane potential was indicated to decrease following luteolin treatment. At the molecular level, luteolin significantly increased the mRNA expression of Bax and the protein expression of cytochrome c, caspase-3, p47phox and p22phox. The results revealed that luteolin decreased Bcl-2 protein expression and inhibited the nuclear localization of Nrf2. In conclusion, the current study indicated that luteolin inhibited HT29 cell proliferation and induced apoptosis via the mitochondrial pathway.

Layer-by-layer assembly of polyelectrolyte films improving cytocompatibility to neural cells.

The using of layer-by-layer assembly polyelectrolyte (PE) films has been suggested as a new versatile technique for surface modification aimed at tissue engineering and cell-based chips. In this study, we investigated the surface morphology of the hyaluronic acid (HA)-based PE films deposited on the amino-functionalized glass slides using atomic force microscopy. These thin films (bilayer number <9) were measured to have nanoscale roughness ranging from 10 to 100 nm. Then the primary hippocampal and cortical neural cells were cultured on the PE films, respectively. After 5 days of culturing, the cytocompatibility to neural cells was evaluated by cellular morphology, neurite outgrowth, and microtubule-associated protein 2 expressions. From the present results, the HA-based PE films were found to be able to support neural cell adhesion and neurite development, especially for the polycation-ending films. It is suggested these HA-based multilayer PE films or similar build-ups could thus be used in the future as a way to modify surfaces for nerve scaffolds and neuron-based chips.

Proliferation of neural precursors in the subventricular zone after chemical lesions of the nigrostriatal pathway in rat brain.

The proliferative activity of neural precursors from the subventricular zone (SVZ) was investigated after a unilateral lesion was formed in the nigrostriatal pathway in adult rats. The lesion was formed by unilateral injection of 6-hydroxydopamine (6-OHDA) into the nigrostriatal pathway, and then bromodeoxyuridine (BrdU) was injected (ip) for 4 days or 2 weeks 10 days after the lesion was formed. The rats were killed, and the brain sections were immunohistochemically stained to detect the expression of BrdU, polysialylated neural-cell-adhesion molecule (PSA-NCAM), glial fibrillary acidic protein (GFAP) and tyrosine hydroxylase (TH) in the SVZ and the striatum (STR). The results showed that the BrdU(+) cells increased significantly in the SVZ, ipsilateral to the lesion at 2 weeks after the lesion. The PSA-NCAM(+) and GFAP(+) cells were also increased in the SVZ at this time. Some BrdU-labeled cells were seen in the same side of the STR and were double-labeled with PSA-NCAM. These cells had a tendency to migrate from the SVZ to the STR. The number of positive cells decreased at 4 weeks after the lesion was formed. The number of nigrostriatal projections with TH(+) decreased significantly in the STR on the lesion side, and the level of decrease was related to the quantity of BrdU-labeled cells at 2 weeks. These results indicate that the neural precursors in the SVZ of adult rats may increase after a lesion has been formed in the nigrostriatal pathway, and these cells might migrate into the STR on the same side.

Hyaluronic acid hydrogel modified with nogo-66 receptor antibody and poly-L-lysine to promote axon regrowth after spinal cord injury.

The biomaterials used for central nervous system injury require not only interacting with specific cell adhesion but also specific growth factor receptors to promote nerve regeneration. In this study, hyaluronic acid (HA)-based hydrogels modified with poly-L-lysine (PLL) and nogo-66 receptor antibody (antiNgR) (HA-PLL/antiNgR) were administered to rats after lateral hemisection of the spinal cord. Anti-neurofilament positive axons were found to extend into the HA-PLL/antiNgR hydrogel at 8 weeks after implantation, which shows significant difference compared with HA-PLL or blank control group. Electron micrographs of implanted hydrogels showed that there were more cells and normal axons with myelin in the HA-PLL/antiNgR implant than that of HA-PLL hydrogel. The antiNgR grafted on HA hydrogels could be detected for 8 weeks after transplantation in vivo. All of these properties may facilitate HA-PLL/antiNgR hydrogels to become a promising scaffold for repairing spinal cord injury. Nevertheless, both two kinds of modified hydrogels (HA-PLL/antiNgR and HA-PLL) showed remarkable advantages in supporting angiogenesis, and simultaneously inhibiting the formation of glial scar.

Preparation and characterization of fibroin/hyaluronic acid composite scaffold.

Hyaluronic acid (HA) was added into fibroin solution to prepare fibroin-based porous composite scaffolds. HA exhibited important effects on pore formation and hydrophilicity of fibroin-based scaffold. The aqueous-fibroin/HA scaffolds had highly homogeneous and interconnected pores with porosity of above 90% and controllable pore size ranging from 123 to 253 microm. The water take-up of fibroin/HA scaffolds increased significantly with the increase of HA content. Containing HA at a defined content range, such as 3-6%, fibroin-based scaffolds' affinity to primary neural cells was improved. In 6%HA/fibroin scaffolds, neurosphere-forming cell migrated from their original aggregate and adhered tightly to the surface of scaffolds.