This work investigated the design parameters necessary for the build and use of an in vitro artificial mouth model built for dental erosion research. It also ascertained the working knowledge of dentists concerning the Human Tissue Act (HTA) and explored an alternative tissue for erosion-testing to human enamel. The design inputs for the artificial mouth were acquired by an innovative observational study conducted upon human volunteers and used in the decisions made in the setting of the fluids’ kinematic behaviour and how the associated devices were to function. This novel system was sought to mimic the interaction of saliva and the dental substrate during the process of consuming an erosive beverage. The model allows researchers to gather data using customizable experimental diets without the technical burden of dealing with a non-realistic regime. The design and build of the artificial mouth model along with its associated equipment and parameters are described and a manual for operation of the model is appended. The device is designed on a fully adjustable multitask basis in which the operator can set several variables such as the desirable salivary kinematic behaviour, offensive beverage flow rate, and volume of consumption. This, subsequently, allows the samples preloaded on the system to be tested for surface characteristics (i.e. surface hardness and surface profilometry) to determine the extent of erosion if any. The model also allows the resultant solution to be analysed for traces of calcium and phosphate ions. To validate the capabilities of the artificial mouth system a set of diets was performed repeatedly. The high degree of agreement and the consistency of results showed that the model is able to mimic realistic scenarios and is capable of producing reliable, reproducible and accurate outcomes. Ostrich eggshell proved to be a potential alternative erosion substrate which is fortuitous as the lack of knowledge on the HTA had meant human enamel was less readily available.

Embryonic stem cells (ESC) constitute a promising source of cells for cardiac transplantation strategies. However, complexities associated with in vivo studies have made it difficult to develop a thorough understanding of cell integration. We have engineered an in vitro system that recapitulates the native cardiac environment using 300μm thick collagen scaffolds seeded with neonatal cardiomyocytes (CM) and electrical field stimulation. The injection of undifferentiated ESC served as a baseline to assess the validity of studying cell transplantation in this model. Yfp-ESC survived and proliferated over several days in model tissue. ESC were not observed to significantly differentiate into the cardiac lineage, and did not integrate with the cardiac cell population. While the injection of ESC improved cardiac cell number, tissue functional properties were hindered. The methods developed herein can be readily adapted to study ESC derived progenitor and differentiated cells, to elucidate the optimal cell state for ESC-mediated cell therapy.

Embryonic stem cells (ESC) constitute a promising source of cells for cardiac transplantation strategies. However, complexities associated with in vivo studies have made it difficult to develop a thorough understanding of cell integration. We have engineered an in vitro system that recapitulates the native cardiac environment using 300μm thick collagen scaffolds seeded with neonatal cardiomyocytes (CM) and electrical field stimulation. The injection of undifferentiated ESC served as a baseline to assess the validity of studying cell transplantation in this model. Yfp-ESC survived and proliferated over several days in model tissue. ESC were not observed to significantly differentiate into the cardiac lineage, and did not integrate with the cardiac cell population. While the injection of ESC improved cardiac cell number, tissue functional properties were hindered. The methods developed herein can be readily adapted to study ESC derived progenitor and differentiated cells, to elucidate the optimal cell state for ESC-mediated cell therapy.

Malaria remains a serious concern for people living and traveling to warm climates in Africa, Asia, and some parts of America. Understanding the mechanism of the malaria parasite in the liver phase could lead to important discoveries for preventative and treatment therapeutics before the disease develops into the blood stage. While in vitro liver cell culture models have been explored, a device that mimics the liver cell architecture with the capability of high-resolution imaging has never been created. In this research, a cell culture microfluidic device was designed and fabricated with a membrane integrated design to mimic the architecture of a liver, cell chamber dimensions affable for high-resolution imaging, and fluidic port design for optical access to both sides of the membrane for the study of malaria parasite invasion.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20978号 / 医博第4324号 / 新制||医||1026(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 井上 治久, 教授 木村 剛, 教授 瀬原 淳子 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Every 37 seconds, someone in the United States dies from cardiovascular disease. Vascular calcification is one of the underlying causes of these fatal events. Medial calcification develops following arteriosclerosis, or hardening of the arteries. Medial calcification is characterized by the deposition of hydroxyapatite in the medial layer of the arteries after normal vascular smooth muscle cells undergo a phenotypic switch to resemble osteoblast-like cells. It is hypothesized that this switch is caused by the wingless related (WNT)-Signaling pathway. The WNT-Signaling pathway, upon activation, causes the upregulation of osteogenic markers for the development of osteoblast-like cells. Current treatments alleviate consequences of calcification but do not address the disease. Due to a lack of cures for calcification, a novel therapy for this disease is overdue. By studying human aortic smooth muscle cells and confirming the role of WNT-Signaling as it relates to calcification, a possible therapeutic target for calcification can be identified.

Cerebral aneurysms occur due to the ballooning of blood vessels in the brain. Rupture of aneurysms can cause a subarachnoid hemorrhage, which, if not fatal, can cause permanent neurologic deficits. Minimally invasive neurovascular devices, such as embolization coils and flow diverters, are methods of treatment utilized to prevent aneurysm rupture. The rapidly growing market for neurovascular devices necessitates the development of accurate aneurysm models for preclinical testing. In vivo models, such as the rabbit elastase model, are commonly chosen for preclinical device testing; however, these studies are expensive, and aneurysm geometries are difficult to control and often do not replicate the variety of geometries found in clinical cases. A promising alternative for preclinical testing of neurovascular devices is an aneurysm blood vessel mimic (aBVM), which is an in vitro tissue-engineered model of a human blood vessel composed of an electrospun scaffold with an aneurysm geometry and human vascular cells. Previous work in the Cal Poly Tissue Engineering Lab has established a process for creating different aneurysm scaffolds based on the shape of different geometries, and this work aimed to further advance these aneurysm geometries in order to enhance the versatility of the in vitro model. The overall goal of this thesis was to customize the aBVM model through variations of different dimensions and to validate the scaffold variations for neurovascular device testing. First, a literature review was performed to identify critical ranges of aneurysm neck diameters and heights that are commonly seen in rabbit elastase models and in human clinical settings in order to set a foundation for creating new geometries. Based on the results, aneurysm geometries with varying neck sizes and heights were modeled and molded, and scaffolds were fabricated through electrospinning. Methods were developed to characterize scaffolds with internal measurements through imaging techniques using a scanning electron microscope. To validate these scaffolds for use as aBVMs for neurovascular device testing, constructs were created by dual-sodding human endothelial cells and smooth muscle cells into scaffolds with varying neck sizes. Finally, flow diverters were deployed in constructs with varying neck sizes in order to evaluate feasibility and initial healing. Customized aneurysm scaffolds can eventually be used with a variety of device studies for screening of neurovascular devices or as a predecessor for in vivo preclinical testing.

Intravenously delivered cancer drugs face transport limitations at the tumor site and cannot reach all parts of tumors at therapeutically effective concentrations. Transport limitations also prevent oxygen from distributing evenly in tumors resulting in hypoxia, which plays a critical role in cancer progression. In this dissertation, I present the development of micro-devices that mimic transport limitations of drugs and nutrients on three dimensional tumor tissues, enable visualization and quantification of the ensuing gradients, and enable simple analysis and mathematical modeling of obtained data. To measure the independent effects of oxygen gradients on tumor tissues, an oxygen delivery device that used microelectrodes to generate oxygen directly underneath three-dimensional tumor cylindroids was developed. Supplying oxygen for 60 hours eliminated the necrotic region typically found in the center of cylindroids. Dead cells were observed moving away from the location of oxygen delivery. These measurements show that oxygen gradients are an important determinant of cell viability and rearrangement. Another micro-device was developed to mimic the delivery and systemic clearance of therapeutic agents. This microfluidic device consisted of cuboidal tumor tissue subjected to continuous medium perfusion along one face. The device was used to measure the spatiotemporal dynamics of the accumulation of therapeutic bacteria in tumors. Suspensions of Salmonella typhimurium and Escherichia coli strains were delivered to tumor tissues for 1 hour. Bacterial motility strongly correlated (R2 = 99.3%) with the extent of tissue accumulation. Based on spatio-temporal profiles and a mathematical model of motility and growth, bacterial dispersion was found to be necessary for deep penetration into tissue. These results show that motility is critical for effective distribution of bacteria in tumors. The microfluidic device was further used to mimic the delivery and clearance of equal concentrations of doxorubicin and liposome-encapsulated doxorubicin (Doxil). A pharmacokinetic/pharmacodynamic model incorporating mechanisms of tissue-level diffusion and binding was developed and experimental data was fit to this model. Doxorubicin was found to have the optimal diffusivity and binding for maximizing therapeutic effect. Doxil was severely limited by low intratumor drug release. These results show that in-vitro models mimicking tissue-level transport limitations more accurately predict the therapeutic response of drugs.

No description available.