Oligodendrocyte Precursor Cells Support Blood-Brain Barrier Integrity via TGF-β Signaling

Trophic coupling between cerebral endothelium and their neighboring cells is required for the development and maintenance of blood-brain barrier (BBB) function. Here we report that oligodendrocyte precursor cells (OPCs) secrete soluble factor TGF-β1 to support BBB integrity. Firstly, we prepared conditioned media from OPC cultures and added them to cerebral endothelial cultures. Our pharmacological experiments showed that OPC-conditioned media increased expressions of tight-junction proteins and decreased in vitro BBB permeability by activating TGB-β-receptor-MEK/ERK signaling pathway. Secondly, our immuno-electron microscopic observation revealed that in neonatal mouse brains, OPCs attach to cerebral endothelial cells via basal lamina. And finally, we developed a novel transgenic mouse line that TGF-β1 is knocked down specifically in OPCs. Neonates of these OPC-specific TGF-β1 deficient mice (OPC-specific TGF-β1 partial KO mice: PdgfraCre/Tgfb1flox/wt mice or OPC-specific TGF-β1 total KO mice: PdgfraCre/Tgfb1flox/flox mice) exhibited cerebral hemorrhage and loss of BBB function. Taken together, our current study demonstrates that OPCs increase BBB tightness by upregulating tight junction proteins via TGF-β signaling. Although astrocytes and pericytes are well-known regulators of BBB maturation and maintenance, these findings indicate that OPCs also play a pivotal role in promoting BBB integrity

Amorphous titanium-oxide supercapacitors with high capacitance

An amorphous titanium-oxide film oxidized anodically on amorphous Ti–10at%V–15at%Si alloy ribbons demonstrated excellent electric properties. Specifically, it showed a remarkable increase in parallel capacitance Cp, series capacitance Cs, time constant RCs, and decrease in the dielectric loss with decreasing frequency. The oblate semicircle after a semicircle with a Warburg region in the Nyquist diagram and rapid increases in the real impedance in the low-frequency region in the Bode diagram demonstrated a parallel circuit comprising an electric transport resistance Re (0.64 MΩ), and a high electric double-layer capacitance Cdl (604.0 μF/cm 2) at a nanometer-sized (${\sim}53\ \text{nm}$ in convex size) uneven surface between an upper (Ti0.84V0.11Si0.05)O1.655 layer approximately 45-nm deep and air. The superior capacitances could be elucidated by electrostatic induction of a large positive charge to the uneven oxide surface based on the electronic conduction state derived from TiO2/VO2 nanostructural interfaces in the upper oxide layer

In Vitro Construction of Scaffold-Free Bilayered Tissue-Engineered Skin Containing Capillary Networks

Many types of skin substitutes have been constructed using exogenous materials. Angiogenesis is an important factor for tissue-engineered skin constructs. In this study, we constructed a scaffold-free bilayered tissue-engineered skin containing a capillary network. First, we cocultured dermal fibroblasts with dermal microvascular endothelial cells at a ratio of 2 : 1. A fibrous sheet was formed by the interactions between the fibroblasts and the endothelial cells, and capillary-like structures were observed after 20 days of coculture. Epithelial cells were then seeded on the fibrous sheet to assemble the bilayered tissue. HE staining showed that tissue-engineered skin exhibited a stratified epidermis after 7 days. Immunostaining showed that the epithelium promoted the formation of capillary-like structures. Transmission electron microscopy (TEM) analysis showed that the capillary-like structures were typical microblood vessels. ELISA demonstrated that vascularization was promoted by significant upregulation of vascularization associated growth factors due to interactions among the 3 types of cells in the bilayer, as compared to cocultures of fibroblast and endothelial cells and monocultures

Proposed model for OPC-BBB interaction.

<p>Trophic coupling between OPCs and cerebral endothelium may play an important role in the BBB function. TGF-β1 may mediate the cell-cell interaction; i.e. OPCs secrete TGF-β1, which then binds to its receptor, followed by activating MEK/ERK pathway to increase the BBB tightness.</p

OPC-derived TGF-β1 and BBB integrity in vivo.

<p><b>A.</b> The OPC-specific TGF-β1 partial or total KO mice showed hemorrhage at post-natal day 0–1. <b>B–C.</b> IgG staining showed that in the OPC-specific TGF-β1 partial or total KO mice, IgG was leaked from blood vessels into brain parenchyma. Green: IgG, Orange: Lectin (endothelial marker), scale bar = 100 µm. Mean + SD of n = 4–5, *p<0.05 vs control group. <b>D.</b> The OPC-specific TGF-β1 deficient mice exhibited BBB leakages (IgG staining) and aberrant ZO-1 structures.</p

TGF-β1 expression in vascular-related brain cells.

<p>Immunostaining confirmed no clear differences in TGF-β1 expression in (<b>A</b>) cerebral endothelium assessed by CD31 staining, (<b>B</b>) astrocytes assessed by GFAP staining, and (<b>C</b>) pericytes assessed by PDGF-R-β staining at post-natal day 0 in the OPC-specific TGF-β1 deficient mice (OPC-specific TGF-β1 partial KO mice: <i>Pdgfra^Cre</i>/<i>Tgfb1^flox/wt</i> mice or OPC-specific TGF-β1 total KO mice: <i>Pdgfra^Cre</i>/<i>Tgfb1^flox/flox</i> mice).</p

MEK/ERK pathway mediates the roles of OPC-derived TGF-β1 in enhancing in vitro BBB integrity.

<p><b>A.</b> OPC-CM treatment (30 min) increased the levels of phospho-ERK1/2 in cerebral endothelial RBE.4 cells, and both the TGF-β receptor inhibitor SB431542 (10 µM) and a MEK/ERK inhibitor U0126 (10 µM) blocked the ERK1/2 phosphorylation by OPC-CM. <b>B–D.</b> U0126 cancelled the supporting effects of OPC-CM on the BBB tightness in our in vitro model. Mean + SD of n = 3, *p<0.05 vs control (OPC-CM: −, U0126: −), #P<0.05 vs OPC-CM only (OPC-CM: +, U0126: −). <b>E.</b> LDH assay showed that the MEK/ERK inhibitor U0126 (10 µM) did not affect endothelial viability. Mean ± SD of n = 3.</p