Browsing by Subject "cell migration"

Now showing 1 - 6 of 6
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    Characterization of Glioblastoma and T Cell Migration in Brain Tissue
    (2023-07) Anderson, Sarah
    Glioblastoma (GBM) is an aggressive malignant brain tumor with extremely low 5-year survival rates. One key characteristic of the disease is the ability of glioblastoma cells to migrate rapidly and spread throughout healthy brain tissue. To develop treatments that effectively target cell migration, it is important to understand the fundamental mechanism driving cell migration in brain tissue. In the first part of this dissertation, we utilized confocal imaging to measure traction dynamics and migration speeds of glioblastoma cells in mouse organotypic brain slices to identify that the cells are using a motor-clutch mode of migration. In addition, both integrins and CD44, as well as myosin motors, were found to play an important role in constituting the adhesive clutch. In developing a treatment that targets migration of glioblastoma cells, it is critical to take into account how this could impact T cell migration and the resulting ability of T cells to kill cancer cells. A hallmark of glioblastoma is the suppression of the immune response, allowing the tumor to grow and spread faster, and infiltration of cytotoxic CD8+ T cells into the tumor has been shown to be an important indicator of disease progression and survival. In the second part of this dissertation, we use mouse organotypic brain slices co-cultured with CD8+ T cells to image migrating CD8+ T cells in healthy brain tissue in response to cell migration targeting drugs and antibodies. We find an increase in migration speed in response to targeting CD44, which is a critical deviation between cancer cell and T cell phenotype, implicating CD44 as a potential target for improving glioma outcomes by slowing cancer cell migration and speeding up CD8+ T cells.
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    Development of Biomimetic Microfluidic Platforms for Cellular Interaction Studies
    (2016-08) Wu, Xiaojie
    Achieving a better understanding of cellular interactions with other critical components in physiological microenvironments is an urgent challenge due to the fact that critical cellular behaviors are delicately regulated by the complexity of the biological system. Factors influencing cellular behaviors include interactions with the surrounding cell types and biological molecules, as well as a range of biophysical factors, such as pressure, flow, and chemical gradients. With a better understanding of environmental impacts on cellular behaviors, mechanistic insights on the pathogenesis of diseases and advances in medical treatment will be provided. Because the technical difficulties of traditional cell assays have limited the systematic study of cellular interactions, novel platforms with the ability to represent cellular interactions in a quick, spatiotemporal-resolved, and biomimetic manner would be welcomed by the research community. Microfluidics, one of the novel techniques used frequently for cell biology studies, is able to introduce the cellular interactions into an in vivo-like microenvironment with high spatiotemporal resolution, also allowing the quantification of cellular behaviors at the single cell level. The aim of this thesis is to develop biomimetic microfluidic platforms to mechanistically study cellular interactions in the context of different biological processes. First, Chapter 1 of this thesis reviews the application of microfluidics in the field of cellular interactions with focus on advances of microfluidics in single cell analysis and in vivo-like microenvironment generation. The following chapters separately discuss the topics including cell-drug interactions (Chapter 2), cell migration within complex gradient patterns (Chapter 3), the interactions between iii cell migration and angiogenesis growth (Chapter 4), heterotypic cellular interactions in a biomimetic environment (Chapter 5), and the effects of shear rates on cellular adhesion behaviors (Chapter 6). In Chapter 2, we developed a microfluidic platform containing stable chemical gradients to assess the drug effects on neutrophil migration, which is the key characteristic of inflammatory diseases. By tracking the migration of single neutrophils, we achieved quantification of various parameters, including average velocity, orientation, and overall effectiveness of migration. In addition to examining neutrophil migratory behaviors, the cytotoxicity of drug candidates was also evaluated to reveal a comprehensive understanding about the drug effects on neutrophil function. In Chapter3 and 4, we continued to study neutrophil migration in more complicated in vivo-like microenvironments. To be specific, a three-dimensional endothelial cell layer was cultured in the microfluidic channel, and neutrophil transendothelial migration was monitored under various chemical gradient patterns such that the competitive and synergistic effects among different cytokine molecules were determined. Furthermore, the interactions between neutrophil migration and endothelial angiogenesis were studied by inducing angiogenic growth of the endothelial cell layer in the microfluidic channel. We found that larger endothelial cell angiogenic growth area induced significantly more neutrophil migration while the process of neutrophil migration was able to stabilize the endothelial cell structure even in the presence of an angiogenesis inhibitor that decreases the angiogenic growth of endothelial cells. After detailed evaluation of neutrophil migration in different conditions, a biomimetic microfluidic model was used in Chapter 5 to study heterotypic cellular interactions between endothelial cells and HeLa cancer cells. Three critical environmental factors, including chemical gradients, flow rate, and hypoxia, were separately introduced into the microfluidic model to determine the effect of each factor on cellular interactions. Also, all these three factors were combined together into a single microfluidic device to investigate the overall effects on cellular interactions, which provides an in vitro approach to predict the cellular behaviors in the context of cancer. In the last chapter (Chapter 6), a simple microfluidic system was established to explore the relationship between shear rates and cell adhesion behaviors. Two major blood cell types, platelets and neutrophils, were injected through the endothelial cell covered-microfluidic channels with different dimensions, and the results suggest that the expression of receptor molecules participating in the cell adhesion is selective to the dimension of microfluidic channel. This conclusion reveals the novel insights on the mechanisms of cell adhesion in various shear rate conditions and provides deeper understandings about the pathogenesis of blood-based diseases. Overall, the research presented in this thesis focuses on using microfluidic platforms to characterize cellular interactions with biological complexity, in hopes of advancing our understanding about cellular behaviors in the pathogenesis of relevant diseases. All the findings reported in this thesis indicate that the application of microfluidic platform enables the recapitulation of in vivo physiological microenvironments and predicts the cellular behaviors occurring in human body, successfully bridging the gap between current in vitro and in vivo approaches.
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    Mathematical Modeling of Cell Migration: Mechanisms in Dictyostelium discoideum.
    (2023-03) Felix, Bryan
    This study aims to understand the biochemical pathways involved in the cytoskeleton of Dictyostelium discoideum, particularly the self-organization process of actin structures. While previous models have explored protein dynamics in various contexts, they tend to oversimplify the underlying biochemical mechanisms. This study presents two extended models that offer updated insights into the chemical interactions and feedback mechanisms of Dictyostelium discoideum. The first model explores how bistability emerges from the topology of the underlying network, while the second model focuses on the mechanisms of filopodia initiation and the role of membrane curvature in their emergence.
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    Microtubule-based control of glioma cell migration mechanics
    (2018-08) Prahl, Louis
    Cell migration underlies the extensive tissue invasion that drives brain tumor (glioma) progression. Glioma cell migration involves the coordinated mechanical functions of the actin cytoskeleton, myosin motors, and substrate adhesions through a biophysical motor-clutch model. Although computational forms of the motor-clutch model predict glioma cell migration behaviors as a function of tissue stiffness, less is known about how other cellular structures such as microtubules influence migration. Presently, a number of microtubule-targeting agents (MTAs) are used to treat various cancers (including gliomas) so understanding their mechanism of action is necessary in order to develop better therapies. In this dissertation, I show that two commonly used MTAs (paclitaxel and vinblastine) each have distinct and nearly opposite effects on traction forces that motor-clutch simulations predict, and which correlate with changes to microtubule organization and dynamics. Effects of MTAs are consistent with influencing F-actin assembly and nucleation rates of protrusions, which impairs the ability of glioma cells to spontaneously polarize and migrate. Microtubule-dependent signaling networks that are perturbed in MTA-treated cells support novel roles for receptor tyrosine kinase (RTK) signaling pathways in mediating these effects. In the final study, we use microfabricated channels that replicate geometric and mechanical features of brain tissue alongside simulation-based methods to study confined glioma cell migration. Simulations recapitulate the dynamics of glioma cell migration in microchannels, as well as accurate predictions of the effects of MTAs and other pharmacological inhibitors of motor-clutch system components. This provides novel evidence for motor-clutch-based cell migration in confinement. In summary, this dissertation identifies specific mechanisms by which microtubules regulate motor-clutch based migration of glioma cells, and outlines a systems-level physics-based approach for understanding anti-motility therapy.
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    Pathway to metastasis: carcinoma dissemination via organized collagen tracks
    (2017-12) Ray, Arja
    A vital part of the metastatic cascade that leads to cancer-related deaths is the initial dissemination of cancer cells from a confined lesion into neighboring tissue by migration and invasion. Breast and pancreatic carcinomas are often associated with increased deposition of collagen-I, which can assemble into aligned fiber tracks in mature breast tumors. Such aligned tracks provide contact guidance cues for directed cancer cell migration and dissemination leading to increased invasion, metastasis and decreased disease-free survival in breast cancer patients. Using multiphoton imaging, we demonstrate that organized collagen architectures develop in the pancreatic ductal adenocarcinoma (PDA) stroma even at the pre-invasive stage with single cells and multicellular clusters interacting with aligned collagen tracks in vivo. Mimicking the collagen patterns with microfabricated substrates, we show that for single cells, aligned architectures induce constrained focal adhesion maturation and associated F-actin alignment, consequently orchestrating anisotropic traction stresses that drive cell orientation and directional migration. While such interactions allow single mesenchymal-like cells to spontaneously “sense” and follow topographic alignment, intercellular interactions within epithelial clusters counteract anisotropic cell-substratum forces, resulting in substantially lower directional response. Indeed, anisotropic cell-substratum interactions from organized periductal collagen may contribute to cell extrusion and dissemination from pre-invasive ductal epithelia in PDA. Such contact guided spreading of cancer cells may be inhibited by dismantling the fiber architecture, diminishing its density or by abrogating cell-ECM interactions. To validate our findings in 3D we engineered novel in vitro substrates using a simple method to align 3D collagen gels by guided cellular compaction, to produce highly aligned, acellular collagen constructs as a controlled microenvironment in vitro. Additionally, we integrated the aligned collagen matrices to cell dense tumor-like plugs, allowing tracking of the temporal evolution of the advancing invasion fronts over several days. Live cell imaging and analysis of 3D cell migration revealed profoundly enhanced motility in aligned collagen matrices for the putative cancer stem cell subpopulation. Heterogeneity in cell migration behavior was also observed between cells at the leading edge and those within the tumor boundary, thus demonstrating the versatility of these platforms in capturing the dynamics of contact guided carcinoma dissemination.
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    Signaling Extraordinaire: Extracellular vesicles in cranial neural crest migration
    (2022-05) Gustafson, Callie
    Extracellular vesicles (EVs) are membrane-bound particles released from all cells that have thus far been examined. Commonly studied in cancer biology, many categories of EVs have been characterized. EVs serve as a means of cell-cell communication across short and long distances. Cells also extend membranous protrusions to communicate and connect with distant cells, and developmental studies show they can serve as highways or conduits for the transfer of EVs. While cancer biology often lacks the context of a physiological system, developmental biology struggles to properly characterize EVs and protrusions. Neural crest cells (NCC) are an ideal system for bridging these fields because invasive cancer reactivates neural crest developmental programs, including epithelial to mesenchymal transition (EMT) and migration. Using cranial neural fold cultures, we identify two types of NCC-derived EVs: exosomes and migrasomes. Upon inhibition of exosome secretion, NCC migration is disrupted, leading to rounder, less motile cells. This data suggests NCC exosomes are critical for migration.