Wei Tan, Ph.D. - US grants

Identifying a certain cell type based on a specific signature, separating cell mixtures according to cellular differences, and studying changes in a specific signature with cell environments are important techniques in biological research. While various biochemical markers of cells have been extensively used for decades, biomechanical properties such as cell stiffness are increasingly recognized as an important indicator of cell type and physiological state. The mechanical properties of cells are defined by the membrane, cytoskeleton and the volume of the cell, and are likely associated with basic characteristics including type, growth, stage of differentiation, and response to the environment. Existing mechanical characterization tools, however, can only examine a few cells at a time, severely limiting their utility and application due to the low throughput associated with the sequential isolation and probing of individual cells.
Here, a high-throughput method will be developed, where optical-based mechanical ?stretching? forces are applied to cells in microfluidic devices. By the end of this 3-year project, a device capable of the rapid measurement of cell mechanical properties will be built and tested on bovine blood cells, vascular cells, and human HeLa cells. A number of broader impacts are expected including providing new research opportunities for undergraduate students, new teaching opportunities at the high-school level, and new recruitment efforts for underrepresented groups within the state of Colorado.

DESCRIPTION (provided by applicant): While much of the Pi's previous research has been peripherally related to biomedicine, it was all done as an engineer's approach to solve biomedical problems, focusing on development of new engineering approaches (i.e. materials, fluidic device, imaging techniques, and mechanical conditioning) to tackle tissue in vitro from a viewpoint of mechanical engineering, based on only a basic understanding of biomedical situation. The proposed training opportunity would provide the PI with an in-depth knowledge of vascular pathology, cell signal transduction, animal and clinical experimentation, as well as added knowledge in imaging, fluid dynamics and mechanobiology in the context of vascular medicine. The career development plan proposed here will greatly help the PI grow in a trans-disciplinary field at the intersection of flow dynamics, cell molecule biology, and vascular medicine. Arterial stiffening is recognized as an important factor of cardiovascular events and increased arterial pulse pressure, a direct consequence of stiffening, has been used to guide pharmaceutical treatment for a variety of systemic vascular diseases. The overall hypothesis of the research project is that increased stiffness of large pulmonary arteries contributes to structural and functional alterations in distal pulmonary arteries, characteristics of pulmonary arterial hypertension, and stiffened arteries play such a pathogenic role in vascular diseases via the modulation of flow pulsatility which causes and/or perpetuates inflammation and thrombosis in the distal PA circulation. To test this hypothesis, three specific aims will be studied: (1) Determine the relationship between pulmonary arterial stiffness and flow pulsatility in hierarchical pulmonary vasculature;(2) Determine effects of flow pulsatility on functional activation of PA endothelial cells;and (3) Determine the molecular mechanisms in flow-induced endothelial activation. RELEVANCE (See instructions): This research program will explore a new mechanism to improve understanding pulmonary vascular diseases. Insights into the mechanism may facilitate development of novel diagnostic and therapeutic strategies that offer an improved quality of life and increased survival rate of affected patients. (End of Abstract)

DESCRIPTION (provided by applicant): Loss of function to arteries or the microvasculature, due to diseases such as atherosclerosis, peripheral artery diseases or ischemia, contributes to high morbidity and high mortality in the U.S. An emerging solution is mesenchymal stem cell (MSC) therapy, which has the potential to regenerate blood vessels and revolutionize the treatment of vascular diseases. However, results from MSC-based vascular therapies have been inconsistent, and worse, some studies have reported vascular dysfunction. These therapeutic outcomes are, at least in part, attributable to an ill-defined cell environment, which ultimately regulates MSC fate during therapy. To achieve successful MSC-based vascular therapy, several unresolved issues must be addressed: (a) suboptimal MSC environments that result in a mixed cell populations with low vascular specificity or signaling; (b) lack of mechanistic understandings as to how multifactorial environments determine MSC fate in vivo; and (c) limited platform technologies available for the translation of in vitro cell differentiatio environments to in vivo vascular therapies. To address these knowledge gaps, the overall goal of this proposal is to establish a comprehensive platform that recapitulates the synergism of the physical and biochemical environments in normal vascular tissues in order to perpetuate highly specific and mature vascular differentiation of MSCs for vascular therapy. Our hypothesis is that vessel-mimetic mechanical and biochemical environments provide synergistic signaling to MSCs, perpetuating vascular regeneration under physiological conditions in vitro and in vivo. To pursue our hypothesis, we will take an innovative approach by developing 3D nanofibrous niches with independently modulated microenvironment factors, i.e. matrix rigidity, ligand and cytokine, to optimize vascular cell regeneration, and incorporating these distinct niches into a graft scaffold with spatiotemporal control for evaluation under physiological flow. This approach is built on our team's biomaterial capabilities of producing nanofibrous materials with controlled rigidity, anisotropy and spatiotemporal release of proteins, and ligand incorporation. Three aims are proposed here: AIM 1 focuses on MSC-matrix interaction mechanisms underlying the rational design of 3D synthetic niche matrices for vascular differentiation; AIM 2 seeks to define synthetic niches that converge mechano-chemical signaling for optimal vascular regeneration; and AIM 3 integrates and evaluates synthetic niches with vascular grafts to demonstrate feasibility and provide critical feedback for future design and clinical translation. This new interdisciplinary study, combining biomaterials, cell signaling, vascular mechanobiology and tissue engineering, if successful, will help to accomplish our long-term goal of designing application-specific vascular microphysiological systems that can predict, improve and optimize cell-based vascular therapy.