Sindrome di Down e fattori di rischio nel declino neurocognitivo

Down syndrome (DS) or Trisomy 21, occurring in 1/700 and 1/1000 livebirths, is the most common genetic disorder, characterized by a third copy of the human chromosome 21 (Hsa21). DS is associated with various defects, including congenital heart diseases, craniofacial abnormalities, immune system dysfunction, mental retardation (MR), learning and memory deficiency. The phenotypic features in DS are a direct consequence of overexpression of genes located within the triplicated region on Hsa21. In addition to developmental brain abnormalities and disabilities, people with DS by the age of 30-40 have a greatly increased risk of early-onset of Alzheimer’s disease (AD) and an apparent tendency toward premature aging. Many of the immunological anomalies in DS can be enclosed in the spectrum of multiple signs of early senescence. People with DS have an increased vulnerability to oxidative damage and many factors, including amyloid beta protein (Abeta), genotype ApoE4, oxidative stress, mutations in mitochondrial DNA (mtDNA), impairment of antioxidant enzymes, accelerated neuronal cell apoptosis, are related to neuronal degeneration and early aging in DS. SUBJECTS and METHODS: Since 2007 a population of 50 adolescents and adults with DS, 26 males and 24 females (sex-ratio: M/F = 1.08), has been evaluated for the presence of neurological features, biomarkers and genetic factors correlated with neuronal degeneration and premature aging. The control group was determined by the mother and the siblings of the patients. A neuropsychiatric evaluation was obtained from all patients. The levels of thyroid antibodies (antiTg and antiTPO) and of some biochemical markers of oxidative stress, including homocysteine (tHcy), uric acid, cobalamin, folate were measured. All patients, the mother and the siblings were genotyped for ApoE gene. RESULTS: 40% of patients, with a mild prevalence of females aged between 19 and 30 years, showed increased levels of antiTg and antiTPO. The levels of tHcy were normal in 52% patients and mildly increased in 40%; hyperomocysteinemia was associated with normal levels of thyroid antibodies in 75% of patients (p<0.005). The levels of uric acid were elevated in 26%. Our study showed a prevalence of severe MR in patients aged between 1-18 years and over 30 years. Only 3 patients, 2 females and one male, over 30 years of age, showed dementia. According to the literature, the rate of Down left-handers was high (25%) compared to the rest of population and the laterality was associated with increased levels of thyroid antibodies (70%). 21.5% of patients were ApoE4 positive (ApoE4+) with a mean/severe MR. CONCLUSIONS: Until now no biochemical evidence of oxidative damage and no deficiency or alteration of antioxidant function in our patients with DS were found. mtDNA sequencing could show some mutations age-related and associated with oxidative damage and neurocognitive decline in the early aging of DS. The final aim is found predictive markers of early-onset dementia and a target strategy for the prevention and the treatment of diseases caused by oxidative stress. REFERENCES: 1) Rachidi M, Lopes C: “Mental retardation and associated neurological dysfunctions in Down syndrome: a consequence of dysregulation in critical chromosome 21 genes and associated molecular pathways.” - Eur J Paediatr Neurol. May;12(3):168-82 (2008). 2) Lott IT, Head E: “Down syndrome and Alzheimer's disease: a link between development and aging.” - Ment Retard Dev Disabil Res Rev, 7(3):172-8 (2001). 3) Lee HC, Wei YH: “Oxidative Stress, Mitochondrial DNA Mutation, and Apoptosis in Aging.” - Exp Biol Med (Maywood), May;232(5):592-606 (2007).

Role of Notch signalling in human hepatocellular carcinoma

The Notch signalling is a cellular pathway that results conserved from Drosophila to Homo sapiens controlling a wide range of cellular processes in development and in differentiated organs. It induces cell proliferation or differentiation, increased survival or apoptosis, and it is involved in stemness maintainance. These functions are conserved, but exerted with a high tissue and cellular context specificity. Signalling activation determs nuclear translocation of the receptor’s cytoplasmic domain and activation of target genes transcription. As many developmental pathway, Notch deregulation is involved in cancer, leading to oncogenic or tumour suppressive role depending on the functions exerted in normal tissue. Notch1 and Notch3 resulted aberrantly expressed in human hepatocellular carcinoma (HCC) that is the more frequent tumour of the liver and the sixth most common tumour worldwide. This thesis has the aim to investigate the role of the signalling in HCC, with particular attention to dissect common and uncommon regulatory pathways between Notch1 and Notch3 and to define the role of the signalling in HCC. Nocth1 and Notch3 were analysed on their regulation on Hes1 target and involvement in cell cycle control. They showed to regulate CDKN1C/p57kip2 expression through Hes1 target. CDKN1C/p57kip2 induces not only cell cycle arrest, but also senescence in HCC cell lines. Moreover, the involvement of Notch1 in cancer progression and epithelial to mesenchymal transition was investigated. Notch1 showed to induce invasion of HCC, regulating EMT and E- Cadherin expression. Moreover, Notch3 showed specific regulation on p53 at post translational levels. In vitro and ex vivo analysis on HCC samples suggests a complex role of both receptors in regulate HCC, with an oncogenic role but also showing tumour suppressive effects, suggesting a complex and deep involvement of this signalling in HCC.

Computational modelling of human stem cell-derived cardiomyocytes - Texture descriptors for biological image processing

This thesis investigates two distinct research topics. The main topic (Part I) is the computational modelling of cardiomyocytes derived from human stem cells, both embryonic (hESC-CM) and induced-pluripotent (hiPSC-CM). The aim of this research line lies in developing models of the electrophysiology of hESC-CM and hiPSC-CM in order to integrate the available experimental data and getting in-silico models to be used for studying/making new hypotheses/planning experiments on aspects not fully understood yet, such as the maturation process, the functionality of the Ca2+ hangling or why the hESC-CM/hiPSC-CM action potentials (APs) show some differences with respect to APs from adult cardiomyocytes. Chapter I.1 introduces the main concepts about hESC-CMs/hiPSC-CMs, the cardiac AP, and computational modelling. Chapter I.2 presents the hESC-CM AP model, able to simulate the maturation process through two developmental stages, Early and Late, based on experimental and literature data. Chapter I.3 describes the hiPSC-CM AP model, able to simulate the ventricular-like and atrial-like phenotypes. This model was used to assess which currents are responsible for the differences between the ventricular-like AP and the adult ventricular AP. The secondary topic (Part II) consists in the study of texture descriptors for biological image processing. Chapter II.1 provides an overview on important texture descriptors such as Local Binary Pattern or Local Phase Quantization. Moreover the non-binary coding and the multi-threshold approach are here introduced. Chapter II.2 shows that the non-binary coding and the multi-threshold approach improve the classification performance of cellular/sub-cellular part images, taken from six datasets. Chapter II.3 describes the case study of the classification of indirect immunofluorescence images of HEp2 cells, used for the antinuclear antibody clinical test. Finally the general conclusions are reported.

Environmental influence on the phenotype: Morphological variation in human dentition

This work is about the role that environment plays in the production of evolutionary significant variations. It starts with an historical introduction about the concept of variation and the role of environment in its production. Then, I show how a lack of attention to these topics may lead to serious mistakes in data interpretation. A statistical re-analysis of published data on the effects of malnutrition on dental eruption, shows that what has been interpreted as an increase in the mean value, is actually linked to increase of variability. In Chapter 3 I present the topic of development as a link between variability and environmental influence, giving a review of the possible mechanisms by which development influences evolutionary dynamics. Chapter 4 is the core chapter of the thesis; I investigated the role of environment in the development of dental morphology. I used dental hypoplasia as a marker of stress, characterizing two groups. Comparing the morphology of upper molars in the two groups, three major results came out: (i) there is a significant effect of environmental stressors on the overall morphology of upper molars; (ii) the developmental response increases morphological variability of the stressed population; (iii) increase of variability is directional: stressed individuals have increased cusps dimensions and number. I also hypothesized the molecular mechanisms that could be responsible of the observed effects. In Chapter 5, I present future perspectives for developing this research. The direction of dental development response is the same direction of the trend in mammalian dental evolution. Since malnutrition triggers the developmental response, and this particular kind of stressor must have been very common in our class evolutionary history, I propose the possibility that environmental stress actively influenced mammals evolution. Moreover, I discuss the possibility of reconsidering the role of natural selection in the evolution of dental morphology.