Bioderived dyes-mediated vat photopolymerization 3D printing of chitosan hydrogels for tissue engineering

The importance of 3D printable hydrogels is constantly increasing in the field of tissue engineering, due to their characteristic structure and similarity with the human body extracellular matrix (ECM). Herein, Quinizarin-based bioderived photoactive dyes were employed for the 3D printing of methacrylated chitosan by vat pho-topolymerization (VPP). Dyes are commonly needed in VPP to obtain good resolution avoiding the light scattering in the vat, here the bioderived molecules had further utility granting the printability with good resolution while acting both as photosensitizers and fillers/crosslinkers. Defined and detailed architectures in the range of millimetres were obtained with low printing times showing for the first time the possibility to obtain all-chitosan 3D structures with suspended features by Digital Light Processing (DLP), which is a form of vat photopolymerization; such a result is not achievable without the quinizarin-derived dyes. The same structures were achieved with an opti-mized concentration of poly(ethylene glycol) diacrylate, as a comparison, enhancing the resolution. For all the formulations, the important feature to obtain the gel printability (considering reactiveness, viscosity, shear thinning behaviour, mechanical properties and stability) were evaluated. The hydrogels mechanical character-ization and swelling properties were also tested and reported. Lastly, the possible application in tissue engi-neering was also evaluated through cell proliferation analysis over samples, including metabolic activity and DNA contempt assays. The use of such bioderived photoactive molecules that simultaneously act as photosensitizer enhancing the ink reactivity, as dye improving the definition of the final structures and as filler/crosslinker increasing the me-chanical stability, could represent a valuable route for the DLP printing of soft hydrogels

Lowering β-Amyloid Levels Rescues Learning and Memory in a Down Syndrome Mouse Model

β-amyloid levels are elevated in Down syndrome (DS) patients throughout life and are believed to cause Alzheimer's disease (AD) in adult members of this population. However, it is not known if β-amyloid contributes to intellectual disability in younger individuals. We used a γ-secretase inhibitor to lower β-amyloid levels in young mice that model DS. This treatment corrected learning deficits characteristic of these mice, suggesting that β-amyloid-lowering therapies might improve cognitive function in young DS patients

Differential Regulation of the Variations Induced by Environmental Richness in Adult Neurogenesis as a Function of Time: A Dual Birthdating Analysis

Adult hippocampal neurogenesis (AHN) augments after environmental enrichment (EE) and it has been related to some of the anxiolytic, antidepressant and neuroprotective effects of EE. Indeed, it has been suggested that EE specifically modulates hippocampal neurogenic cell populations over the course of time. Here we have used dual-birthdating to study two subpopulations of newborn neuron in mice (Mus musculus): those born at the beginning and at the end of enrichment. In this way, we demonstrate that while short-term cell survival is upregulated after an initial 1 week period of enrichment in 2 month old female mice, after long-term enrichment (2 months) neither cell proliferation nor the survival of the younger newly born cell populations are distinguishable from that observed in non-enriched control mice. In addition, we show that the survival of older newborn neurons alone (i.e. those born at the beginning of the enrichment) is higher than in controls, due to the significantly lower levels of cell death. Indeed, these parameters are rapidly adjusted to the sudden cessation of the EE conditions. These findings suggest both an early selective, long-lasting effect of EE on the neurons born in the initial stages of enrichment, and a quick response when the environment again becomes impoverished. Therefore, EE induces differential effects on distinct subpopulations of newborn neurons depending on the age of the immature cells and on the duration of the EE itself. The interaction of these two parameters constitutes a new, specific regulation of these neurogenic populations that might account for the long-term enrichment's behavioral effects

Characterization of PTZ-Induced Seizure Susceptibility in a Down Syndrome Mouse Model That Overexpresses CSTB

Down syndrome (DS) is a complex genetic syndrome characterized by intellectual disability, dysmorphism and variable additional physiological traits. Current research progress has begun to decipher the neural mechanisms underlying cognitive impairment, leading to new therapeutic perspectives. Pentylenetetrazol (PTZ) has recently been found to have positive effects on learning and memory capacities of a DS mouse model and is foreseen to treat DS patients. But PTZ is also known to be a convulsant drug at higher dose and DS persons are more prone to epileptic seizures than the general population. This raises concerns over what long-term effects of treatment might be in the DS population. The cause of increased propensity for epilepsy in the DS population and which Hsa21 gene(s) are implicated remain unknown. Among Hsa21 candidate genes in epilepsy, CSTB, coding for the cystein protease inhibitor cystatin B, is involved in progressive myoclonus epilepsy and ataxia in both mice and human. Thus we aim to evaluate the effect of an increase in Cstb gene dosage on spontaneous epileptic activity and susceptibility to PTZ-induced seizure. To this end we generated a new mouse model trisomic for Cstb by homologous recombination. We verified that increasing copy number of Cstb from Trisomy (Ts) to Tetrasomy (Tt) was driving overexpression of the gene in the brain, we checked transgenic animals for presence of locomotor activity and electroencephalogram (EEG) abnormalities characteristic of myoclonic epilepsy and we tested if those animals were prone to PTZ-induced seizure. Overall, the results of the analysis shows that an increase in Cstb does not induce any spontaneous epileptic activity and neither increase or decrease the propensity of Ts and Tt mice to myoclonic seizures suggesting that Ctsb dosage should not interfere with PTZ-treatment

Prompt K_short production in pp collisions at sqrt(s)=0.9 TeV

The production of K_short mesons in pp collisions at a centre-of-mass energy of 0.9 TeV is studied with the LHCb detector at the Large Hadron Collider. The luminosity of the analysed sample is determined using a novel technique, involving measurements of the beam currents, sizes and positions, and is found to be 6.8 +/- 1.0 microbarn^-1. The differential prompt K_short production cross-section is measured as a function of the K_short transverse momentum and rapidity in the region 0 < pT < 1.6 GeV/c and 2.5 < y < 4.0. The data are found to be in reasonable agreement with previous measurements and generator expectations.Comment: 6+18 pages, 6 figures, updated author lis

Synaptic vesicle recycling is unaffected in the Ts65Dn mouse model of Down syndrome

Down syndrome (DS) is the most common genetic cause of intellectual disability, and arises from trisomy of human chromosome 21. Accumulating evidence from studies of both DS patient tissue and mouse models has suggested that synaptic dysfunction is a key factor in the disorder. The presence of several genes within the DS trisomy that are either directly or indirectly linked to synaptic vesicle (SV) endocytosis suggested that presynaptic dysfunction could underlie some of these synaptic defects. Therefore we determined whether SV recycling was altered in neurons from the Ts65Dn mouse, the best characterised model of DS to date. We found that SV exocytosis, the size of the SV recycling pool, clathrin-mediated endocytosis, activity-dependent bulk endocytosis and SV generation from bulk endosomes were all unaffected by the presence of the Ts65Dn trisomy. These results were obtained using battery of complementary assays employing genetically-encoded fluorescent reporters of SV cargo trafficking, and fluorescent and morphological assays of fluid-phase uptake in primary neuronal culture. The absence of presynaptic dysfunction in central nerve terminals of the Ts65Dn mouse suggests that future research should focus on the established alterations in excitatory / inhibitory balance as a potential route for future pharmacotherapy

Behavioral, cognitive and biochemical responses to different environmental conditions in male Ts65Dn mice, a model of Down syndrome.

Ts65Dn mouse is the most widely accepted model for Down syndrome. We previously showed that environmental enrichment improved spatial learning in female but deteriorated it in male Ts65Dn mice. This study analyzed the factors contributing to the disturbed cognition of male Ts65Dn mice after enriched housing, by allocating male control and Ts65Dn mice in four conditions after weaning: small (n = 2-3) and large group (n = 8-10) housing, and enriched housing in small (2-3) and large groups (8-10). Learning, aggressive behavior, anxiety-like behavior and biochemical correlates of stress were evaluated when Ts65Dn and control mice were 4-5 months old. Environmental enrichment in large mixed colonies of Ts65Dn and diploid littermates disturbed behavioral and learning skills of Ts65Dn mice in the Morris water maze. ACTH and testosterone levels were not modified in any group of mice. Ts65Dn and control mice subjected to enriched housing in large groups and Ts65Dn mice housed in large groups showed higher corticosterone levels. Aggressive behavior was evaluated by measuring the number of attacks performed in the presence of an intruder. Ts65Dn mice performed less attacks than controls in all conditions, especially after enriched housing, indicating subordination. In the plus maze, cognitive aspects (i.e. risk assessment) and motor components (open arm avoidance) of anxiety behavior were evaluated; no difference in any condition was found. It is suggested that an excess of social and/or physical stimulation in Ts65Dn mice may affect cognition by disturbing the emotional and behavioral components of the learning process

Differential effects of environmental enrichment on behavior and learning of male and female Ts65Dn mice, a model for Down syndrome.

We have assessed the effects of enriched environment (EE) upon behavioral and cognitive performances of partially trisomic Ts65Dn (TS) mice and their control (CO) littermates. Enriched environment was applied to pups for 7 weeks after weaning. Circadian spontaneous activity (actimetry), exploratory behavior (hole board), activity in the open field and spatial memory (Morris Water Maze, repeated acquisition and cued paradigms) were analyzed in 86 female and 75 male mice, starting 15 days after completing enrichment. For each gender, mice were distributed in non-enriched and enriched control and trisomic groups. Enriched environment reduced in trisomic females and enhanced in trisomic males\u27 circadian activity. Exploratory behavior was increased by enrichment in all groups, regardless of gender or presence of trisomy. In the Morris Water Maze, a significant improvement of the spatial memory was observed in enriched-control females, but not in enriched-control male mice, as assessed by distances traveled. Performances in the four groups of control animals were also consistently and significantly better than those of matching trisomic mice. In the acquisition trials, enrichment improved performance in trisomic female animals, but deteriorated in trisomic male mice. In all groups, changes in escape latencies and distances induced by enrichment were accounted for by changes in the total time spent in the periphery of the pool, indicating changes in learning strategy. Working memory was the function more affected by enrichment. It is concluded that enriched environment induces behavioral and learning changes in trisomic mice, although gender plays a significant modulatory role

Alterations of neocortical pyramidal cell phenotype in the Ts65Dn mouse model of Down syndrome: Effects of environmental enrichment

Mental retardation in individuals with Down syndrome (DS) is thought to result from anomalous development and function of the brain; however, the underlying neuropathological processes have yet to be determined. Early implementation of special care programs result in limited, and temporary, cognitive improvements in DS individuals. In the present study, we investigated the possible neural correlates of these limited improvements. More specifically, we studied cortical pyramidal cells in the frontal cortex of Ts65Dn mice, a partial trisomy of murine chromosome 16 (MMU16) model characterized by cognitive deficits, hyperactivity, behavioral disruption and reduced attention levels similar to those observed in DS, and their control littermates. Animals were raised either in a standard or in an enriched environment. Environmental enrichment had a marked effect on pyramidal cell structure in control animals. Pyramidal cells in environmentally enriched control animals were significantly more branched and more spinous than non-enriched controls. However, environmental enrichment had little effect on pyramidal cell structure in Ts65Dn mice. As each dendritic spine receives at least one excitatory input, differences in the number of spines found in the dendritic arbors of pyramidal cells in the two groups reflect differences in the number of excitatory inputs they receive and, consequently, complexity in cortical circuitry. The present results suggest that behavioral deficits demonstrated in the Ts65Dn model could be attributed to abnormal circuit development