Academic literature on the topic '4D development'

SPÉCIFICATION DU DESTIN CELLULAIRE DES CELLULES SOUCHES MAMMAIRES EN 4DAu cours du développement, une coordination entre la spécification du destin cellulaire et la morphogenèse tissulaire est nécessaire à la formation des organes. Par conséquent, la façon dont différents types de cellules se différencient dans le temps et l'espace reste une question majeure en biologie du développement.La glande mammaire est constituée d'un épithélium ramifié composé d'une couche externe de cellules basales (BCs) et d'un compartiment interne de cellules luminales (LCs). Dans ce tissu, l'homéostasie adulte est exclusivement maintenue par des progéniteurs unipotents, alors que des cellules souches mammaires multipotentes (MaSC) ne se trouvent que dans la glande embryonnaire, ce qui en fait un paradigme tissulaire idéal pour étudier leur comportement dynamique et leur contribution à la morphogenèse tissulaire.HYPOTHÈSE DE TRAVAILNous avons récemment montré que les cellules souches mammaires deviennent unipotentes lors de la tubulogenèse de la glande, suggérant un lien étroit entre spécification cellulaire et morphogenèse. Notre hypothèse implique que la perte de multipotence soit liée aux remaniements cellulaires qui guident la morphogenèse. Cependant, le moment exact et les mécanismes responsables du passage de la multipotence à l'unipotence sont encore inconnus.OBJECTIF ET MÉTHODOLOGIEL'objectif principal de ce projet était d'intégrer les circuits transcriptionnels définissant le potentiel de différenciation des cellules souches à l'analyse de la morphogenèse cellulaire et tissulaire en temps réel, afin de déchiffrer les mécanismes qui sous-tendent l'acquisition de l'identité cellulaire et d'étudier la coordination entre spécification des cellules souches et morphogenèse. Nous avons abordé cet objectif ambitieux en combinant deux approches : 1) des analyses transcriptomiques en cellule unique intégrées dans l’espace, au cours du développement mammaire, et 2) une approche de suivi du lignage en temps réel dans des cultures mammaires embryonnaires ex vivo, afin d'étudier les comportements et réarrangements cellulaires au cours des premières phases de la croissance mammaire.RÉSULTATSNous avons constaté que la restriction du potentiel des cellules souches est progressive pendant le développement embryonnaire. Par transcriptomique sur cellules uniques, nous avons pu distinguer trois types cellulaires distincts très tôt (E15). L'intégration dans l’espace de ces données transcriptomiques nous a révélé que des cellules de type BC et LC sont positionnées différemment dans le bourgeon mammaire très précocement. Cette analyse a donc révélé de nouveaux marqueurs moléculaires des LC et BC embryonnaires, qui ne peuvent pas être distingués avec les marqueurs mammaires adultes connus.De plus, nous avons défini les signatures transcriptionnelles qui distinguent deux populations de cellules stromales mammaires embryonnaires délimitées dans l'espace. Nous avons aussi montré qu’une signalisation paracrine du mésenchyme aux cellules épithéliales, via Fgf10-Fgfr2, influence la morphogenèse de la glande mammaire.Nous avons ensuite développé une approche d’analyse d’images semi-automatique aux niveaux cellulaire et tissulaire dans nos explants mammaires analysés par microscopie time-lapse. Nous montrons que les étapes initiales de la morphogenèse sont caractérisées par des réarrangements cellulaires très dynamiques. De plus, l'activation épithéliale de la beta-catenin empêche la formation de branches, indiquant que Wnt est un régulateur essentiel de la morphogenèse mammaire.Ces travaux mettent en lumière les circuits transcriptionnels qui régissent le branchement mammaire et qui lient la différenciation des cellules souches à leur dynamique cellulaire pendant la morphogenèse. Les mécanismes ainsi dévoilés nous fournissent des biomarqueurs potentiels du cancer du sein, qui résulte souvent de la réactivation de programmes de multipotence embryonnaires<br>DEFINING CELL FATE SPECIFICATION OF MOUSE MAMMARY STEM CELLS IN 4DCoordination of cell fate specification and branching morphogenesis is necessary to generate an organ with its specialized final structure and function. Accordingly, how different cell types are specified in a tightly regulated manner in time and space, in order to drive the morphogenesis of a complex tissue, remains a major question in the field of developmental biology.The mammary gland (MG) consists in a branched bi-layered epithelium composed of an outer layer of basal cells (BCs) and an inner compartment of polarised luminal cells (LCs). In this tissue, adult homeostasis is exclusively maintained by lineage-restricted unipotent progenitors, whereas multipotent mammary stem cells (MaSCs) are only found in the embryonic gland, making it an ideal tissue paradigm to study stem cell dynamics and lineage specification, as well as their contribution to tissue morphogenesis.WORKING HYPOTHESISOur recent results showed that multipotent MaSCs become lineage-restricted around embryonic day E15.5, coinciding with the first morphogenetic events that establish the mammary ductal network. We thus hypothesized that loss of multipotency in the mammary gland was linked to cell rearrangements, leading to the branching of embryonic mammary buds. However, the exact timing and the mechanisms responsible for the switch from multipotency to unipotency during embryonic MG are still unknown.AIM AND METHODOLOGYThe overarching aim of this project was to characterise the stem cell dynamics underlying MaSCs differentiation during MG development, and to define the transcriptional signals underpinning this process. We have approached this ambitious objective combining two approaches: 1) single-cell RNA sequencing analysis at different embryonic times, to discover which signals determine cell identity during mammary development, and 2) a live lineage tracing approach in ex vivo embryonic mammary cultures to study dynamic cell behaviours and rearrangements during the earliest phases of mammary growth.RESULTSWe found that lineage restriction is a progressive developmental process. By single cell transcriptomics, we identified a single population of mammary epithelial cells at E13.5, but we could distinguish three transcriptionally distinct cell subsets at E15.5, which included luminal-like, basal-like and hybrid cells co-expressing luminal and basal genes. Spatial transcriptomic analysis revealed that the basal-like and luminal-like clusters were indeed already spatially restricted in the embryonic mammary bud, being positioned either in close proximity to the basement membrane or in the inner bud region, respectively. Importantly, this analysis revealed novel molecular markers of committing LCs and BCs, that cannot be distinguished with known adult MG markers.Additionally, we report the transcriptional signatures distinguishing two spatially restricted embryonic mammary mesenchymal cell populations, representing sub-epithelial and dermal mesenchyme. Long-term live-imaging revealed that paracrine signalling from embryonic mesenchyme to epithelial cells, via Fgf10-Fgfr2, influences epithelial branching.We then developed a deep learning-based pipeline to semi-automatically track individual cells and tissue branches in embryonic mammary explants analysed by time-lapse microscopy. We show that the initial steps of morphogenesis are characterized by highly dynamic cell rearrangements in the growing branch tips. However, forced activation of the Wnt/b-catenin pathway in the embryonic mammary epithelium precluded branching in vivo and ex vivo, indicating that epithelial Wnt signalling is an essential regulator of mammary branching morphogenesis.This work sheds light on the timing and mechanisms governing mammary cell fate decisions, providing potential biomarkers of breast cancer, which often arises from reactivation of embryonic multipotency programs

Currently in the field of demolition, which generates most of the waste in the construction industry, the treatment of waste largely relies on landfill or degraded recycling, which leads to significant consumption of natural resource and energy and a shortage of landfill site. In order to improve the inefficiency of demolition waste recovery, “to suggest improvements in the environmental impact of the demolition industry in UK” was set as the aim of the present research. After the identification of few opportunities for communication between demolishers and constructers in the current social system, a collaboration support system between these two stakeholders called ‘Demolition Project Mapping’ (DPM) system was suggested. In the system, the impact evaluation tool developed in the 4D-CAD software is applied to the demolition project simulation. This tool allows the users to dynamically simulate the impact of project planning which can be designed in the tool. In the pilot study, the simulation result shows the large potential to reduce the impact (e.g. 28% for the cost) by the tool application.

The recent emergence of super-resolution microscopy imaging techniques has surpassed the diffraction limit to improve image resolution. Contrary to the breakthroughs of spatial resolution, high temporal resolution remains a challenge. This dissertation demonstrates a simple, on axis, 4D (3D + time) multi-colour microscopy imaging (MCMI) technology that delivers simultaneous 3D broadband imaging over cellular volumes, which is especially applicable to the real-time imaging of fast moving biospecimens. Quadratically distorted (QD) grating, in the form of an off axis-Fresnel zone plate, images multiple object planes simultaneously on a single image plane. A delicate mathematical model of 2D QD grating has been established and implemented in the design and optimization of QD grating. Grism, a blazed grating and prism combination, achieves chromatic control in the 4D multi-plane imaging. A pair of grisms, whose separation can be varied, provide a collimated beam with a tuneable chromatic shear from a collimated polychromatic input. The optical system based on QD grating and grisms has been simply appended to the camera port of a commercial microscope, and a few bioimaging tests have been performed, i.e. the 4D chromatically corrected imaging of fluorescence microspheres, MCF-7 and HeLa cells. Further investigation of bioimaging problems is still in progress.

Radiotherapy is a lifesaving cancer treatment using radiation to kill cancer cells. Effective treatment requires accuracy and precision, directing radiation to the cancer while avoiding healthy tissue. As such, in-depth knowledge of the cancer’s size, location and surroundings is required for planning radiation delivery. For regions under motion, such as the thorax, spatial-temporal imaging (4D CT) is required to gain an understanding of how the anatomy will move during treatment. Current 4D CT techniques fail to adapt to a changing patient, resulting in inaccurate images and reduced confidence in treatment planning. This thesis presents the development and implementation of the next generation of 4D CT, patient adaptive CT imaging. Adaptive CT is a software solution that adapts the 4D CT imaging process to patient motion signals (respiratory changes and cardiac function), with the goal of improving image accuracy. There are three main studies around which this body of work focuses. The first outlines steps towards the clinical translation of adaptive CT, comparing adaptive CT to standard 4D CT imaging techniques. The second outlines the development for future applications and improvements of adaptive CT. Delving into limitations of the system itself, an in-silico analysis of the system and scanner parameters on image quality is detailed. The universality of the system is discussed and techniques for inter-brand compatibility are explored. The third details the expansion of adaptive CT for emerging radiation therapy indications. Cardiac motion is incorporated into the adaptive CT software and a detailed feasibility study is presented with implications for centrally located lung cancer and non-invasive cardiac radioablation treatments. Overall, this body of work presents the advancement of patient adaptive CT imaging, providing superior images for radiation therapy treatment planning and opening up 4D CT imaging for new treatment paradigms.

Doutoramento em Nanociências e Nanotecnologia<br>O entrelaçamento de estruturas filamentares marcou um passo importante na evolução da humanidade. Vários tipos de filamentos são usados em tecidos, cordas e, mais recentemente em micro e nanoestruturas. Esta tese oferece um contributo que pode ser relevante para as àreas do têxtil, nanotecnologias e campos relacionados com a ciência dos materiais. Nesta tese, são descritos métodos para produzir micro e nanofibras com diferentes propriedades físicas de acordo com formatos pré-estabelecidos nas estruturas. Alguns destes métodos são inspirados em sistemas naturais, onde as estruturas contêm topologias específicas para ultrapassar diferentes tarefas. Em particular, fibras helicoidais são produzidas experimentalmente usando a técnica de electrofiação. Em segundo lugar, é introduzido uma generalização do conceito das perversões. Perversões são ocorrências geométricas que invertem o sentido de rotação de estruturas helicoidais. As perversões aparecem quando filamentos, com as extremidades constrangidas, enrolam e adoptam formas helicoidal mas têm de conservar a torção total. Mostramos que é possível obter matematicamente e experimentalmente uma variedade contínua de perversões diferentes que apresentam diferentes geometrias. Experimentalmente, diferentes perversões são geradas irradiando microfibras electrofiadas com ciclos de irradiação de luz UV e máscaras opacas. Os resultados experimentais confirmam também que os diferentes tipos de perversões têm comportamentos distintos quando libertadas e adoptam configurações finais diferentes. Do mesmo modo, usando uma abordagem experimental semelhante, são obtidas hélices com diferentes curvaturas alternadamente. É observado que, durante o relaxamento das fibras, as regiões com curvatura intrínseca maior, começam a enrolar primeiro, enquanto as regiões com curvatura intrínseca menor permanecem alongadas até a um ponto em que começam a enrolar depois. Todos os efeitos observados experimentalmente estão em concordância com simulações computacionais realizadas para modelar a dinâmica de filamentos com curvatura intrínseca. Os resultados experimentais e computacionais demonstram que é possível controlar com precisão a forma de microfilamentos modificando as propriedades mecânicas da superfície das fibras, em vez de depender arranjos moleculares específicos. Por último, descrevemos duas abordagens para obter entrelaçamentos com fibras helicoidais usando exclusivamente interacções mecânicas. A ligação nos tecidos é gerada, no primeiro caso, fazendo enrolar as perversões entre os filamentos adjacentes e, no segundo caso, entrelaçando as voltas das hélices dos filamentos. Simulações computacionais mostram como tecidos podem ser gerados com sucesso usando cada uma das ideias para criar ligações entre as fibras.<br>The entanglement of filamentary structures marked an important step in mankind evolution. Filaments appear in fabrics, ropes and, more recently, in micro and nanostructures. This thesis offers a contribution that can be relevant to the fields of textiles, nanotechnologies and materials science in general. In this thesis, we present methods for shaping micro and nanofibres on demand and with different physical properties. Some of these methods are inspired in natural systems, where structures have specific topologies to fulfil different tasks. In particular, it will be discussed how fibres with helical shape can be produced using the electrospinning technique. Secondly, we introduce a generalization of the concept of perversions. Perversions are geometrical occurrences that reverse the handedness of connected helices. Perversions arise when clamped filaments coil into a helical shape but must conserve zero overall twist. We show mathematically and experimentally that a continuous range of different perversions can exist and present different geometries. Experimentally, different perversions are generated by using irradiated micro electrospun fibres with cycles of UV light and opaque masks. Experimental results also confirm that different types of perversions behave differently upon release and adopt different final configurations. We also produce filaments containing helices with alternating curvatures. It is observed that, upon release, the regions with higher curvature start to curl first, while regions with lower intrinsic curvature remain stretched until start to curl later. All the effects observed in experiments is in good agreement with computational simulations performed to model the dynamics of filaments with intrinsic curvature. The experimental and computational results showed that the precise control of the shape of microfilaments can be achieved by changing the properties of the fibres surface, instead of relying on material’s molecular arrangements. Finally, we describe two approaches to entangle helical filaments by using exclusively mechanical interactions. The linkage in fabrics is generated, in the first case, by winding perversions between neighbouring filaments and, in the second case, by intertwining helical loops of the filaments. Computational simulations show how fabrics can be generated by using both approaches to create links between the fibres.