Host-microbe interactions at the gastrointestinal interface have emerged as a key component in the governance of human health and disease. Advances in micro-physiological systems are providing researchers with unprecedented access and insights into this complex relationship. These systems combine the benefits of microengineering, microfluidics, and cell culture in a bid to recreate the environmental conditions prevalent in the human gut. Here we present the human-microbial cross talk (HuMiX) platform, one such system that leverages this multidisciplinary approach to provide a representative in vitro model of the human gastrointestinal interface. HuMiX presents a novel and robust means to study the molecular interactions at the host-microbe interface. We summarize our proof-of-concept results obtained using the platform and highlight its potential to greatly enhance our understanding of host-microbe interactions with a potential to greatly impact the pharmaceutical, food, nutrition, and healthcare industries in the future. A number of key questions and challenges facing these technologies are also discussed. (C) 2017 THE AUTHORS. Published by Elsevier LTD on behalf of the Chinese Academy of Engineering and Higher Education Press Limited Company. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

archives@tulane.edu / 1 / Owen Richfield

The blood-brain barrier (BBB) is composed of brain microvascular endothelial cells (BMECs), pericytes, and astrocytic endfeet, which regulate the transport of molecules into and out of the brain. BMECs possess intrinsic barrier properties that limit the passage of approximately 98% of small molecules into the brain in healthy individuals. However, in some brain diseases, the BBB undergoes structural and functional alterations, which can contribute to disease progression. In this study, we aimed to investigate the BBB by exploring the effects of endothelial cell stretching and the optimal dimensionality of stretching to enhance endothelium barrier tightness in Chapter 2. Subsequently, we developed an endothelium gradient stretching device to further examine the stretching effect in Chapter 3. Additionally, we investigated the promotion of endothelium tightness through the use of electrospun fibers, wherein we controlled the pore size. Based on these findings, we designed and fabricated an organ chip model that incorporates mechanical stretching, microfluidic techniques, electrospun fibers, and hydrogel extracellular matrix (ECM). The results of permeability testing demonstrated that this chip significantly improved the tightness of microvascular selective transport ability and has the potential to be used in drug sorting for central nervous system (CNS) diseases.

archives@tulane.edu / Fibrotic diseases comprise up to 45% of deaths in the industrialized world. Few effective anti-fibrotic therapeutics exist, due in part to the lack of human-relevant preclinical models. The goal of this research was to improve the modeling of fibrotic diseases in microphysiological systems (MPS) by engineering quiescence in cultured human fibroblasts prior to MPS incorporation. To create an assay for testing this approach, a versatile organ chip was designed while optimizing workflow for production of the organ chip molds with an SLA 3D printer. After identifying 2D culture conditions that repress fibroblast activation, we tested the hypothesis that the 2D culture protocol would impact the fibrotic baseline in our MPS. 3D confocal microscopy and multi-metric image analysis of immunostaining for cellular and extracellular matrix (ECM) components via intensity and pattern quantification revealed the establishment of more physiological baseline for MPS fibrosis models. To test in a disease-relevant context, we created a model of the stromal reaction in lung cancer using our organ chip and demonstrated that our integrated MPS can be used to quantify the fibrosis-inducing effects of cancer cells that drive stromal reactions. / 1 / Max Wendell

90% de la mortalité par cancer provient de tumeurs disséminées, ou métastases. Ces métastases se forment à partir de cellules tumorales qui s'échappent d'une tumeur primaire, circulent dans le sang, puis quittent les vaisseaux sanguins pour enfin aller nicher dans des organes distants et former des tumeurs secondaires. Les processus par lesquels ces cellules circulantes envahissent les organes distants, remodèlent leur environnement pour créer une «niche micrométastatique», prolifèrent pour produire des métastases macroscopiques, sont mal connus, principalement en raison d'un manque de modèles expérimentaux. En effet ces événements sont rares, se produisent à une échelle microscopique et à des localisations à priori inconnues. La perte d'adhérence cellulaire des cellules tumorales se détachant des tissus tumoraux primaires est associée à un phénomène de transformation connu sous le nom de transition épithéliale-mésenchymateuse (EMT) conduisant à la perte des caractéristiques épithéliales. Dans ce travail, nous avons souhaité aborder la question du processus métastatiques par l'étude de l'influence de l'étape de circulation dans le flux sanguin sur différentes caractéristiques de cellules tumorales. Pour cela, des modèles microfluidiques contenant des constrictions mécaniques afin d'imiter la microcirculation sanguine ont été conçus et fabriqués. Nous avons soumis des cellules provenant de tumeurs primaires du sein dans des situations de confinement périodiques à l'intérieur de ces canaux microfluidiques en utilisant un système de contrôle de flux. Nous avons étudiés l'impact des déformations induites par les constrictions des canaux microfluidiques sur l'expression génétique des marqueurs EMT, la morphologie ainsi que la dynamique des changements morphologiques. Nous montrons que ces paramètres cellulaires sont touchés par la déformation mécanique imposée sous flux, suggérant que l'étape de circulation des cellules tumorales dans le sang a un rôle important dans la capacité de celles-ci à produire des métastases. / 90% of cancer mortality arises from metastases, due to cells that escape from a primary tumor, circulate in the blood as circulating tumor cells (CTCs), leave blood vessels and nest in distant organs. The processes by which CTCs invade distant organs, remodel their environment to create a “micrometastatic niche”, the eventual triggering of a proliferation leading to a macroscopic metastases, are poorly known, mostly because of a lack of experimental models. These events are rare; occur in the body at unknown places and on a microscopic scale. The loss of cell adhesion of tumor cells detaching from the primary tumor tissues will undergo a transformation phenomenon known as epithelial-to mesenchymal transition (EMT) leading to the loss of epithelial characteristics with different expression patterns of EMT markers (E-cadherin, N-cadherin, Vimentin, Snail1/2, Twist1/2, ZEB1/2). The changes in mechanical and physical properties of interacting cells during morphological and malignant transformation are investigated and their quantifications measured. Here, microfluidic models containing mechanical constrictions in order to mimic the blood microcirculation have been designed and fabricated. Metastatic breast cancer cells are subjected and confined to the microfluidic channels using a flow control system. These cells are circulated under optimal culture conditions, and monitored in the channels for the observance of biophysical occurrences from continuous mechanical cellular deformations. The biophysical effects of circulation and confinement on tumor cell morphogenesis will be investigated.

Two-dimensional cell culture and animal models inadequately represent human pharmacokinetics and diseases like inflammatory bowel disease and colorectal cancer. This means missed diagnostic and therapeutic opportunities, high drug attrition rates, and a portfolio of approved drugs that underdeliver the desired benefits to patient outcomes. This encourages the development of a more physiologically relevant intestine model. The objective of this work was to develop a 384-well plate organ-on-a-chip platform, IFlowPlateTM, that can accommodate up to 128 human intestine models with accessible lumens and perfusable branched vasculature in an ECM environment. Fibrin-Matrigel® was used a structurally supportive and biologically instructive substrate that enabled: (1) prolonged cell culture (at least 15 days) with routine refreshment of aprotinin-supplemented medium, (2) formation of a confluent Caco-2 monolayer with barrier function, and (3) de novo assembly of a vascular network with barrier function. A fluorescent dextran permeability assay was used for in situ real-time measurements of epithelial barrier function in a high-throughput manner. Mixed co-culture of endothelial cells and fibroblasts in fibrin-Matrigel® resulted in the formation of an interconnected network of patent vessels that retained an albumin surrogate tracer within the luminal space indicating endothelial barrier function. To improve the success rate of anastomoses between living vessels and fluidic channels, the modification of inherently hydrophobic PDMS and polystyrene culture surfaces with ECM protein was explored. To address the limitations of a cancer cell line-derived intestine model, the replacement of Caco-2 cells with biopsied-derived colon organoid cells was investigated. Different gel formulations were assessed for their ability to induce colon organoid fragments to form monolayers. Finally, the incorporation of multiscale intestinal topography and luminal flow was considered through a modified approach to plate fabrication, whereby moulded alginate is embedded in ECM and sacrificed to generate a scaffold. Work to make the moulded alginate more robust is presented. / Thesis / Master of Applied Science (MASc) / Two-dimensional cell culture and animal models inadequately represent human drug metabolism and diseases like inflammatory bowel disease and colorectal cancer. The objective of this work is to develop a more physiologically relevant human intestine model. Using fabrication techniques pioneered by the semiconductor industry, a custom organ-on- a-chip platform in the format of a 384-well plate was developed. This platform is compatible with standard laboratory equipment and practices and can accommodate up to 128 human intestine models comprised of the intestinal epithelium and associated network of blood vessels. In this platform, the cells of the intestinal epithelium and vasculature are supported by a network of natural proteins. This allows processes like vessel growth to be modelled in this platform. Vessel growth plays a key role in the progression of inflammatory bowel disease and cancer, and this model could help scientists better understand these diseases.

The research presented in this dissertation supports the overall goal of producing sensor functionalized neural microphysiological systems to enable deeper fundamental understandings of disease pathology and to provide drug screening and discovery platforms for improved clinical translation. Towards this goal, work addressing three broad objectives has been completed. The first objective was expanding the manufacturing process capabilities for hydrogels and tissues through augmentation of the 3D printing systems and developing novel modeling capabilities. The second objective was to expand the palette of available materials which exhibit the rheological properties required for 3D printing and the mechanical and biological properties required for neural tissue culture. The third objective was to develop sensing capabilities for both monitoring and control of the manufacturing process and to provide non-destructive assessment of microphysiological systems in real-time to quantify the dynamics of disease progression or response to treatment. The first objective of process improvement was addressed both through modification of the 3D printing system itself and through modeling of process physics. A new manifold was implemented which enabled on-the-fly mixing of bioprinting inks (bioinks) to produce smooth concentration gradients or discrete changes in concentration. Modeling capabilities to understand the transport occurring during both the processing and post-processing windows were developed to provide insight into the relationship between the programmed concentration distribution and its temporal evolution and stability. Vacuum-based pick-and-place capabilities for integration of prefabricated components for sensing and stimulation into the printed hydrogel constructs were developed. Models of the stress profiles, which relate to cell viability, within the printing nozzle during extrusion were produced using parameters extracted from rheological characterization of bioinks. The second objective was addressed through the development hydrogel bioinks which exhibited yield stresses without the use of rheological modifiers (fillers) to enable 3D printing of free-standing neural tissue constructs. A hybrid bioink was developed using the combination of a synthetic polaxamer with biomacromolecules present in native neural tissue. Functionalization of the biomacromolecules with catechol or methacrylate groups enabled two crosslinking mechanisms: chelation and UV exposure. Crosslinked gels exhibited moduli in the range of native neural tissue and enabled high viability culture of multiple neural cell types. The third objective was addressed through the characterization and implementation of physical and electronic sensors. The resonance of millimeter-scale dynamic-mode piezoelectric cantilevers submerged in polymer solutions was found to persist into the gel phase enabling viscoelastic sensing in hydrogels and monitoring of sol-gel transitions. Resonant frequency and quality factor of the cantilevers were related with the viscoelastic properties of hydrogels through both a first principles approach and empirical correlation. Electrode functionalized hollow fibers were implemented as impedimetric sensors to monitor bioink quality during 3D printing. Impedance spectra were collected during extrusion of cell-laden bioinks and the magnitude and phased angle of the impedance response correlated with quality measures such as cell viability, cell type, and stemness which were validated with traditional off-line assays. / Doctor of Philosophy / The research presented in this dissertation supports the overall goal of producing sensor functionalized neural microphysiological systems to enable deeper fundamental understandings of disease pathology and to provide drug screening and discovery platforms for improved clinical translation. Microphysiological systems are miniaturized tissue constructs which strive to mimic the complex conditions present in-vivo within an in-vitro platform. By producing these microphysiological systems with sensing functionality, new insight into the mechanistic progression of diseases and the response to new treatment options can be realized. Towards this goal, work addressing three broad objectives has been completed. The first objective was expanding the manufacturing process capabilities for hydrogels and tissues through augmentation of the 3D printing systems and developing novel modeling capabilities. The second objective was to expand the palette of available materials which exhibit both the properties required for 3D printing and the mechanical and biological properties required for neural tissue culture. The third objective was to develop sensing capabilities for both monitoring and control of the manufacturing process and to provide non-destructive assessment of microphysiological systems in real-time to quantify the dynamics of disease progression or response to treatment. Through these efforts higher quality microphysiological systems may be produced benefitting future researchers, medical professionals, and patients.

Endothelial cells, EC, are the cell type closest to the blood stream in vessel walls. These cells can affect the origin of atherosclerosis, plaques clogging the vessels. The behaviour of EC is affected by neighbouring smooth muscle cells and shear stress from the blood flow. The aim with this thesis was to fabricate a structure for an aorta-on-a-chip that can be used to study these two parameters and their influence on EC and vascular diseases. Previous research using a two-channel system resulted in leakage and low viability of the muscle cells. A three-channel system has therefore been made to include a middle channel with the muscle cells incorporated in a gel. Cell medium is flowed in the outer channels to provide the cells with nutrition. The flow in the channel with EC has been calculated to correspond to the shear stress in an aorta. Membranes of polyethylene terephthalate and polycarbonate were used to divide the channels and both were shown to be compatible with EC. Different bonding procedures were investigated to manufacture leakage-free chips. In the study, adhesive bonding clogged the channels and the parameters for thermal bonding of COC, cyclic olefin copolymer, were not fully optimised. This made chemical bonding with layers of PDMS, polydimethylsiloxane, the best alternative. APTES, (3-Aminopropyl)triethoxysilane, treatment in addition to plasma treatment on the surfaces improved the bonding strength. Polycarbonate membranes got better results in the bonding tests than polyethylene terephthalate. The resulting aorta-on-a-chip was therefore successfully fabricated in PDMS and polycarbonate membranes using plasma and APTES treatment for bonding.

Les particules issues de la pollution sont responsables de millions de morts prématurées. Les nanoparticules (au diamètre inférieur à 100 nm) atteignent les alvéoles où elles rencontrent la barrière alvéolo-capillaire. Cette barrière est composée d'un épithélium alvéolaire et d'un endothélium, dos à dos contre une membrane ultrafine (environ 0.2 µM), soumis à une stimulation constante exercée par l'inflation cyclique des alvéoles et par le cisaillement dû à la circulation sanguine. Nous nous sommes appliqués à développer un modèle in vitro innovant de cette barrière alvéolo-capillaire afin d'observer les interactions des nanoparticules avec cette barrière. Dans un premier temps, nous avons développé un substrat micro-fabriqué qui reproduit les propriétés géométriques et physiques de la membrane alvéolo-capillaire. Sur cette membrane, nous avons mis en place une co-culture de cellules épithéliales alvéolaires (A549) et endothéliales (HUVEC). Grâce à une étude de microscopie confocale, nous avons observé le comportement de ce modèle en termes d'étanchéité et de fonctions biologiques. Finalement nous avons observé les interactions entre des nanoparticules de silice et notre modèle en termes de toxicité, d'internalisation et de translocation. Dans une seconde partie, nous avons développé une puce microfluidique à deux chambres qui permet de reproduire autour de notre modèle de co-culture le microenvironnement spécifique des alvéoles pulmonaires. Des études de conception mécanique et l'optimisation de méthodes de microfabrication nous ont permis de générer une puce réversible compatible avec de la culture à long-terme et de l'observation en live par microscopie confocale. Dans une troisième partie, nous avons commencé un travail préliminaire visant à intégrer des cellules pluripotentes induites différenciées dans notre modèle in vitro. Nous avons travaillé à optimiser deux protocoles de différentiation sur une lignée commerciale: vers un endothélium et vers un épithélium alvéolaire. Finalement, nous proposons ici un modèle in vitro offrant de nombreux avantages: une importante communication intercellulaire via leur co-culture sur une membrane ultrafine, une culture long-terme observable au quotidien, la reproduction des stimuli dynamiques de l'environnement alvéolo-capillaire in vivo et la possibilité d'effectuer des tests d'interaction et de translocation de nanoparticules. / Pollutions particles are responsible for millions of premature death. Nanoparticles (with a diameter below 100 nm) reach the alveolar sacs where they encounter the alveolar capillary barrier. This barrier is constituted of an alveolar epithelium and an endothelium back to back on an ultra-thin membrane (about 0.2 µm), submitted to constant stimuli due to cyclic alveolar inflation and blood flow shear stress. We focused here on developing an innovative in vitro model of the alveolar capillary barrier to study the interactions of the nanoparticles with this barrier. Firstly, we have developed a micro-engineered substrate reproducing the geometrical and physical properties of the alveolar capillary membrane. We implemented the co-culture of an alveolar epithelium (A549) and an endothelium (HUVEC) on this membrane. We used confocal microscopy to observe the behavior of our model regarding barrier integrity and specific phenotypes. Finally, we observed the interactions between Silica nanoparticles and our model in terms of toxicity, internalization and translocation. Secondly, we developed a two-chamber microfluidic chip reproducing the specific microenvironment of the alveoli around our co-culture model. Studies of mechanical design and fabrication processes optimization allowed for the generation of a reversible chip compatible with long-term culture and live observation with a confocal microscope. Thirdly, we launched preliminary experiments aiming at the integration of differentiated induced pluripotent stem cells in our in vitro model. We worked on optimizing two directed differentiation protocols: towards an endothelium and towards an alveolar epithelium.Finally, we present here an in vitro model with numerous features: a close-contact co-culture on an ultra-thin membrane enabling important intercellular communication, a long-term culture allowing for live monitoring, mimicking the in vivo dynamic stimuli of the alveolar capillary barrier microenvironment and the possibility for nanoparticles interaction and translocation studies.

Using a novel, adipose-liver, two-organ, human-on-a-chip system, the metabolic disease non-alcoholic fatty liver disease was modeled. This model was then used to test the effects of the gut microbiome on NAFLD progression. Two products of the gut microbiome, Trimethylamine-n-oxide and butyrate, were selected as representatives of potentially harmful and potentially beneficial compounds. A dose response, adipocyte and hepatocyte monocultures controls, and HoaC systems were run for 14 days. Through this experimentation, it was found that a dysbiosis of the gut microbiome could be influencing NAFLD progression. Additionally, further development and discovery regarding adipose-liver systems was added to the ongoing conversation of HoaC systems and their usages.