NOTCH1 signaling induces pathological vascular permeability in diabetic retinopathy.

Diabetic macular edema is a major complication of diabetes resulting in loss of central vision. Although heightened vessel leakiness has been linked to glial and neuronal-derived factors, relatively little is known on the mechanisms by which mature endothelial cells exit from a quiescent state and compromise barrier function. Here we report that endothelial NOTCH1 signaling in mature diabetic retinas contributes to increased vascular permeability. By providing both human and mouse data, we show that NOTCH1 ligands JAGGED1 and DELTA LIKE-4 are up-regulated secondary to hyperglycemia and activate both canonical and rapid noncanonical NOTCH1 pathways that ultimately disrupt endothelial adherens junctions in diabetic retinas by causing dissociation of vascular endothelial-cadherin from ß-catenin. We further demonstrate that neutralization of NOTCH1 ligands prevents diabetes-induced retinal edema. Collectively, these results identify a fundamental process in diabetes-mediated vascular permeability and provide translational rational for targeting the NOTCH pathway (primarily JAGGED1) in conditions characterized by compromised vascular barrier function.

Differentiation of human embryonic stem cells into cone photoreceptors through simultaneous inhibition of BMP, TGFß and Wnt signaling.

Cone photoreceptors are required for color discrimination and high-resolution central vision and are lost in macular degenerations, cone and cone/rod dystrophies. Cone transplantation could represent a therapeutic solution. However, an abundant source of human cones remains difficult to obtain. Work performed in model organisms suggests that anterior neural cell fate is induced 'by default' if BMP, TGFß and Wnt activities are blocked, and that photoreceptor genesis operates through an S-cone default pathway. We report here that Coco (Dand5), a member of the Cerberus gene family, is expressed in the developing and adult mouse retina. Upon exposure to recombinant COCO, human embryonic stem cells (hESCs) differentiated into S-cone photoreceptors, developed an inner segment-like protrusion, and could degrade cGMP when exposed to light. Addition of thyroid hormone resulted in a transition from a unique S-cone population toward a mixed M/S-cone population. When cultured at confluence for a prolonged period of time, COCO-exposed hESCs spontaneously developed into a cellular sheet composed of polarized cone photoreceptors. COCO showed dose-dependent and synergistic activity with IGF1 at blocking BMP/TGFß/Wnt signaling, while its cone-inducing activity was blocked in a dose-dependent manner by exposure to BMP, TGFß or Wnt-related proteins. Our work thus provides a unique platform to produce human cones for developmental, biochemical and therapeutic studies and supports the hypothesis that photoreceptor differentiation operates through an S-cone default pathway during human retinal development.

Mesoscopic photosystems for solar light harvesting and conversion: facile and reversible transformation of metal-halide perovskites.

Recently, hybrid organic-inorganic metal halide perovskites have gained prominence as potent light harvesters in thin film solid-state photovoltaics. In particular the solar-to-electric power conversion efficiency (PCE) of devices using CH(3)NH(3)PbI(3) as sensitizer has increased from 3 to 20.1% within only a few years. This key material can be prepared by solution processing from PbI(2) and CH(3)NH(3)I in one step or by sequential deposition. In the latter case an electron capturing support such as TiO(2) is first covered with PbI(2), which upon exposure to a CH(3)NH(3)I solution is converted to the perovskite. Here we apply for the first time quartz crystal microbalance (QCMD) measurements in conjunction with X-ray diffraction and scanning electron microscopy to analyse the dynamics of the conversion of PbI(2) to CH(3)NH(3)PbI(3). Employing 200 nm thick PbI(2) films as substrates we discover that the CH(3)NH(3)I insertion in the PbI(2) is reversible, with the extraction into the solvent isopropanol occurring on the same time scale of seconds as the intercalation process. This offers an explanation for the strikingly rapid and facile exchange of halide ions in CH(3)NH(3)PbX(3) by solution processing at room temperature.

Subnanometer Ga2O3 tunnelling layer by atomic layer deposition to achieve 1.1 V open-circuit potential in dye-sensitized solar cells.

Herein, we present the first use of a gallium oxide tunnelling layer to significantly reduce electron recombination in dye-sensitized solar cells (DSC). The subnanometer coating is achieved using atomic layer deposition (ALD) and leading to a new DSC record open-circuit potential of 1.1 V with state-of-the-art organic D-π-A sensitizer and cobalt redox mediator. After ALD of only a few angstroms of Ga(2)O(3), the electron back reaction is reduced by more than an order of magnitude, while charge collection efficiency and fill factor are increased by 30% and 15%, respectively. The photogenerated exciton separation processes of electron injection into the TiO(2) conduction band and the hole injection into the electrolyte are characterized in detail.

In situ investigation of dye adsorption on TiO2 films using a quartz crystal microbalance with a dissipation technique.

Dye adsorption plays a crucial role in dye-sensitized solar cells. Herein, we demonstrate an in situ liquid-phase analytical technique to quantify in real time adsorption of dye and coadsorbates on flat and mesoporous TiO(2) films. For the first time, a molar ratio of co-adsorbed Y123 and chenodeoxycholic acid has been measured.

High-efficiency dye-sensitized solar cell with three-dimensional photoanode.

Herein, we present a straightforward bottom-up synthesis of a high electron mobility and highly light scattering macroporous photoanode for dye-sensitized solar cells. The dense three-dimensional Al/ZnO, SnO(2), or TiO(2) host integrates a conformal passivation thin film to reduce recombination and a large surface-area mesoporous anatase guest for high dye loading. This novel photoanode is designed to improve the charge extraction resulting in higher fill factor and photovoltage for DSCs. An increase in photovoltage of up to 110 mV over state-of-the-art DSC is demonstrated.

Dye-sensitized solar cell based on a three-dimensional photonic crystal.

We present a material assembly route for the manufacture of dye-sensitized solar cells, coupling a high-surface mesoporous layer to a three-dimensional photonic crystal (PC). Material synthesis aided by self-assembly on two length scales provided electrical and pore connectivity at the mesoporous and the microporous level. This construct allows effective dye sensitization, electrolyte infiltration, and charge collection from both the mesoporous and the PC layers, opening up additional parameter space for effective light management by harvesting PC-induced resonances.

The LIM homeobox transcription factor Lhx2 is required to specify the retina field and synergistically cooperates with Pax6 for Six6 trans-activation.

In mammals, a limited set of homeobox-containing transcription factors are expressed in the presumptive eye field and required to initiate eye development. How these factors interact together at the genetic and molecular level to coordinate this developmental process is poorly understood. We found that the Lhx2 and Pax6 transcription factors operate in a concerted manner during retinal development to promote transcriptional activation of the Six6 homeobox-gene in primitive and mature retinal progenitors. Lhx2 demarcates the presumptive retina field at the neural plate stage and Lhx2 inactivation delays initiation of Rx, Six3 and Pax6 expression in this domain. The later expressed Six6 is properly activated in the pituitary/hypothalamic axis of Lhx2(-/-) embryos, but expression fails to be initiated in the optic vesicle. Lhx2 and Pax6 associate with the chromatin at several regions of Six6 in vivo and cooperate for trans-activation of Six6 regulatory elements in vitro. In retinal progenitor/stem cells, both Lhx2 and Pax6 are genetically required for proper Six6 expression and forced co-expression of Lhx2 and Pax6 can synergistically trans-activate the Six6 locus. Our work reveals how two master regulators of eye development coordinate their action to sequentially promote tissue-specific transcriptional initiation and full activation of a retinal determinant gene.

Heterochromatic genome instability and neurodegeneration sharing similarities with Alzheimer's disease in old Bmi1+/- mice.

Sporadic Alzheimer's disease (AD) is the most common cause of dementia. However, representative experimental models of AD have remained difficult to produce because of the disease's uncertain origin. The Polycomb group protein BMI1 regulates chromatin compaction and gene silencing. BMI1 expression is abundant in adult brain neurons but down-regulated in AD brains. We show here that mice lacking one allele of Bmi1 (Bmi1+/-) develop normally but present with age cognitive deficits and neurodegeneration sharing similarities with AD. Bmi1+/- mice also transgenic for the amyloid beta precursor protein died prematurely and present aggravated disease. Loss of heterochromatin and DNA damage response (DDR) at repetitive DNA sequences were predominant in Bmi1+/- mouse neurons and inhibition of the DDR mitigated the amyloid and Tau phenotype. Heterochromatin anomalies and DDR at repetitive DNA sequences were also found in AD brains. Aging Bmi1+/- mice may thus represent an interesting model to identify and study novel pathogenic mechanisms related to AD.

MicroRNA signatures in vitreous humour and plasma of patients with exudative AMD.

Age-related macular degeneration (AMD) is a leading cause of blindness worldwide affecting individuals over the age of 50. The neovascular form (NV AMD) is characterized by choroidal neovascularization (CNV) and responsible for the majority of central vision impairment. Using non-biased microRNA arrays and individual TaqMan qPCRs, we profiled miRNAs in the vitreous humour and plasma of patients with NV AMD. We identified a disease-associated increase in miR-146a and a decrease in miR-106b and miR-152 in the vitreous humour which was reproducible in plasma. Moreover, miR-146a/miR-106b ratios discriminated patients with NV AMD with an area under the Receiver Operating Characteristic curve (ROC AUC) of 0,977 in vitreous humour and 0,915 in plasma suggesting potential for a blood-based diagnostic. Furthermore, using the AMD Gene Consortium (AGC) we mapped a NV AMD-associated SNP (rs1063320) in a binding site for miR-152-3p in the HLA-G gene. The relationship between our detected miRNAs and NV AMD related genes was also investigated using gene sets derived from the Ingenuity Pathway Analysis (IPA). To our knowledge, our study is the first to correlate vitreal and plasma miRNA signatures with NV AMD, highlighting potential future worth as biomarkers and providing insight on NV AMD pathogenesis.

Control and Study of the Stoichiometry in Evaporated Perovskite Solar Cells.

Herein, we present the precise stoichiometric control of methlyammonium lead iodide perovskite thin-films using high vacuum dual-source vapor-phase deposition. We found that UV/Vis absorption and emission spectra were inadequate for assessing precisely the perovskite composition. Alternatively, inductively coupled plasma mass spectrometry (ICP-MS) is used to give precise, reproducible, quantitative measurements of the I/Pb ratio without systematic errors that often result from varying device thicknesses and morphologies. This controlled deposition method enables better understanding of the evaporation and deposition processes; methylammonium iodide evaporation appears omnidirectional, controlled using the chamber pressure and incorporated in the film through interaction with the unidirectionally evaporated PbI2. Furthermore, these thin-films were incorporated into solar cell device architectures with the best photovoltaic performance and reproducibility obtained for devices made with stoichiometric perovskite active layers. Additionally, and particularly pertinent to the field of perovskite photovoltaics, we found that the I-V hysteresis was unaffected by varying the film stoichiometry.

In Situ Mapping of the Molecular Arrangement of Amphiphilic Dye Molecules at the TiO2 Surface of Dye-Sensitized Solar Cells.

Amphiphilic sensitizers are central to the function of dye-sensitized solar cells. It is known that the cell's performance depends on the molecular arrangement and the density of the dye on the semiconductor surface, but a molecular-level picture of the cell-electrolyte interface is still lacking. Here, we present subnanometer in situ atomic force microscopy images of the Z907 dye at the surface of TiO2 in a relevant liquid. Our results reveal changes in the conformation and the lateral arrangement of the dye molecules, depending on their average packing density on the surface. Complementary quantitative measurements on the ensemble of the film are obtained by the quartz-crystal microbalance with dissipation technique. An atomistic picture of the dye coverage-dependent packing, the effectiveness of the hydrophobic alkyl chains as blocking layer, and the solvent accessibility is obtained from molecular dynamics simulations.

Pharmacokinetics of an extended 4-hour infusion of piperacillin-tazobactam in critically ill patients undergoing continuous renal replacement therapy.

STUDY OBJECTIVE: To evaluate the pharmacokinetic and pharmacodynamic profiles of piperacillin-tazobactam administered as a 4-hour infusion in critically ill patients undergoing continuous renal replacement therapy (CRRT). DESIGN: Prospective, observational, pharmacokinetic study. SETTING: Intensive care unit of a tertiary care hospital in Montréal, Canada. PATIENTS: Twenty critically ill adults who were undergoing continuous venovenous hemodiafiltration and receiving a 4-hour infusion of piperacillin 4 g-tazobactam 0.5 g every 8 hours for a documented or suspected infection. INTERVENTION: Blood samples were collected every hour over an 8-hour dosing interval. Prefilter and postfilter blood samples, and effluent and urine samples were also collected. MEASUREMENTS AND MAIN RESULTS: The primary outcome was the proportion of patients who achieved an unbound piperacillin plasma concentration above a target minimum inhibitory concentration (MIC) of 64 mg/L (MIC that inhibits 90% of isolates for Pseudomonas aeruginosa) for at least 50% of the dosing interval; 18 (90%) of the 20 patients achieved this outcome. In all patients, the free piperacillin concentrations were above the Pseudomonas aeruginosa breakpoint of 16 mg/L for the entire time interval. Regarding piperacillin pharmacokinetic parameters, the median (interquartile range) minimum unbound plasma concentration was 65.15 mg/L (51.30-89.30), maximum unbound plasma concentration was 141.3 mg/L (116.75-173.90), sieving coefficient was 0.809 (0.738-0.938), total clearance was 65.82 ml/minute (53.79-102.87), and renal clearance was 0.16 ml/minute (0.05-3.04). The median CRRT dose was 32.0 ml/kg/h (25.0-39.8). CONCLUSIONS: Administration of a 4-hour infusion of piperacillin-tazobactam was associated with a favorable pharmacodynamic profile in patients undergoing CRRT. Concentrations associated with maximal activity were attained in our patients.

Characterization of new transcripts enriched in the mouse retina and identification of candidate retinal disease genes.

PURPOSE: Most retinal disease genes are preferentially expressed in photoreceptors, the light-sensitive cells involved in phototransduction. In addition, some of the genes linked to retinal diseases are essential for normal retinal development. The goal of this study was to identify new transcripts enriched in photoreceptors involved in retinal development or diseases. METHODS: To isolate uncharacterized retinal transcripts, the bioinformatic method Digital Differential Display (DDD) was used. RNA in situ hybridization was used to characterize gene-expression patterns. RESULTS: Twenty-seven mouse ESTs highly represented in retinal libraries were identified. Eight ESTs were predominantly expressed in photoreceptors and/or in the retinal pigment epithelium (RPE), whereas transcripts for other ESTs were detected more ubiquitously in the retinal cells or abundantly in ganglion cells and/or the inner nuclear layer. Mapping of the corresponding human orthologues of the photoreceptor/RPE-enriched genes revealed that two of them are candidate disease genes for retinitis pigmentosa, loci RP22 and RP28. Both of these are predominantly expressed in rod photoreceptors. The candidate RP22 gene codes for a putative transmembrane protein showing homology to Cln8 (ceroid lipofuscinosis, neuronal 8), in which gene mutations are associated with photoreceptors degeneration in mice. Also identified were two genes expressed in photoreceptors that are candidate disease genes for recessive Bardet-Biedl syndrome type 3 (BBS3) and recessive ataxia with RP (AXPC1). CONCLUSIONS: This study demonstrates how bioinformatic analysis can be used to identify novel tissue-specific genes relevant to development and diseases.

Mechanical stability enhancement by pore size and connectivity control in colloidal crystals by layer-by-layer growth of oxide.

Control of the pore size and connectivity of micro-sphere colloidal crystal lattices has been achieved by a layer-by-layer growth of silica using atmospheric pressure room temperature chemical vapour deposition of silica, a method which largely increases the mechanical stability of the lattice without disrupting its long range order.

Impedance spectroscopic analysis of lead iodide perovskite-sensitized solid-state solar cells.

Mesoscopic solid-state solar cells based on the inorganic-organic hybrid perovskite CH3NH3PbI3 in conjunction with the amorphous organic semiconductor spiro-MeOTAD as a hole transport material (HTM) are investigated using impedance spectroscopy (IS). A model to interpret the frequency response of these devices is established by expanding and elaborating on the existing models used for the liquid and solid-state dye-sensitized solar cells. Furthermore, the influence of changing the additive concentrations of tert-butylpyridine and LiTFSI in the HTM and varying the HTM overlayer thickness on top of the sub-micrometer thick TiO2 on the extracted IS parameters is investigated. The internal electrical processes of such devices are studied and correlated with the overall device performance. In particular, the features in the IS responses that are attributed to the ionic and electronic transport properties of the perovskite material and manifest as a slow response at low frequency and an additional RC element at intermediate frequency, respectively, are explored.

Inorganic hole conductor-based lead halide perovskite solar cells with 12.4% conversion efficiency.

Organo-lead halide perovskites have attracted much attention for solar cell applications due to their unique optical and electrical properties. With either low-temperature solution processing or vacuum evaporation, the overall conversion efficiencies of perovskite solar cells with organic hole-transporting material were quickly improved to over 15% during the last 2 years. However, the organic hole-transporting materials used are normally quite expensive due to complicated synthetic procedure or high-purity requirement. Here, we demonstrate the application of an effective and cheap inorganic p-type hole-transporting material, copper thiocyanate, on lead halide perovskite-based devices. With low-temperature solution-process deposition method, a power conversion efficiency of 12.4% was achieved under full sun illumination. This work represents a well-defined cell configuration with optimized perovskite morphology by two times of lead iodide deposition, and opens the door for integration of a class of abundant and inexpensive material for photovoltaic application.

Yttrium-substituted nanocrystalline TiO2 photoanodes for perovskite based heterojunction solar cells.

We report the use of Y(3+)-substituted TiO2 (0.5%Y-TiO2) in solid-state mesoscopic solar cells, consisting of CH3NH3PbI3 as the light harvester and spiro-OMeTAD as the hole transport material. A power conversion efficiency of 11.2% under simulated AM 1.5 full sun illumination was measured. A 15% improvement in the short-circuit current density was obtained compared with pure TiO2, due to the effect of Y(3+) on the dimensions of perovskite nanoparticles formed on the semiconductor surface, showing that the surface modification of the semiconductor is an effective way to improve the light harvesters' morphology and electron transfer properties in the solid-state mesoscopic solar cells.

See-through dye-sensitized solar cells: photonic reflectors for tandem and building integrated photovoltaics.

See-through dye-sensitized solar cells with 1D photonic crystal Bragg reflector photoanodes show an increase in peak external quantum efficiency of 47% while still maintaining high fill factors, resulting in an almost 40% increase in power conversion efficiency. These photoanodes are ideally suited for tandem and building integrated photovoltaics.

Neuron-derived semaphorin 3A is an early inducer of vascular permeability in diabetic retinopathy via neuropilin-1.

The deterioration of the inner blood-retinal barrier and consequent macular edema is a cardinal manifestation of diabetic retinopathy (DR) and the clinical feature most closely associated with loss of sight. We provide evidence from both human and animal studies for the critical role of the classical neuronal guidance cue, semaphorin 3A, in instigating pathological vascular permeability in diabetic retinas via its cognate receptor neuropilin-1. We reveal that semaphorin 3A is induced in early hyperglycemic phases of diabetes within the neuronal retina and precipitates initial breakdown of endothelial barrier function. We demonstrate, by a series of orthogonal approaches, that neutralization of semaphorin 3A efficiently prevents diabetes-induced retinal vascular leakage in a stage of the disease when vascular endothelial growth factor neutralization is inefficient. These observations were corroborated in Tg(Cre-Esr1)/Nrp1(flox/flox) conditional knockout mice. Our findings identify a therapeutic target for macular edema and provide further evidence for neurovascular crosstalk in the pathogenesis of DR.