QSpace Community:http://hdl.handle.net/1974/7692015-04-21T09:51:33Z2015-04-21T09:51:33ZInvestigation of adipose-derived stem cells for applications in cardiac regeneration: cell source characterization and the effect of cardiac ECM on cardiomyogenesisRusso, Valeriohttp://hdl.handle.net/1974/127852015-03-19T18:51:54Z2015-03-19T04:00:00ZTitle: Investigation of adipose-derived stem cells for applications in cardiac regeneration: cell source characterization and the effect of cardiac ECM on cardiomyogenesis
Authors: Russo, Valerio
Abstract: Cardiovascular disease is the leading cause of mortality in the world and stem cell therapy has shown promise for its treatment. Focusing on adipose-derived stem cells (ASCs), numerous aspects still need to be investigated, including depot- and donor- dependent differences in ASC characteristics and the cardiomyogenic potential of these cells within the complex microenvironment of the cardiac extracellular matrix (ECM).
In the first part of my thesis, a standardized comparative study was conducted between donor-matched subcutaneous and omentum fat ASCs, as well as donor-matched pericardial fat and thymic remnant ASCs. This study highlighted variability in the yield, viability, immunophenotype, clonogenic potential, doubling time, and adipogenic and osteogenic potential of the ASC populations. More specifically, ASCs isolated from both intrathoracic depots had a significantly higher proportion of CD34+ cells at passage 2. Furthermore, ASCs from subcutaneous and pericardial adipose tissue demonstrated enhanced adipogenic capacity, whereas ASCs isolated from the omentum displayed the highest levels of osteogenic markers in culture. Through cell culture analysis under hypoxic conditions (5% O2), oxygen tension was shown to be a key mediator of colony forming efficiency and osteogenesis for all depots.
In the second stage, non-crosslinked 3-D porous foams derived from decellularized porcine cardiac ECM were developed. Mincing and milling processing methods were explored during scaffold fabrication and the architecture, ECM composition and physical properties of the foams were characterized. The minced foams demonstrated enhanced mechanical properties, improved long-term stability under simulated culturing conditions and better conservation of ECM constituents.
The final stage of experimental work focused on investigating the cardiomyogenic differentiation of pericardial fat ASCs on minced cardiac foams, collagen I gels and tissue culture polystyrene using modified cardiomyogenic medium (MCM) or 5-azacytidine stimulation. Results showed that MCM was more effective than 5-azacytidine in stimulating cardiac gene and protein expression. Furthermore, enhanced differentiation was observed with both treatments on the cardiac foams, suggesting a synergistic effect of the cardiac ECM. Further, the cardiac foams were observed to provide an inductive microenvironment for the ASCs under control medium culture conditions, inducing cardiomyogenic gene and protein expression in the absence of external differentiation factors.
Description: Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2015-03-19 13:17:57.262015-03-19T04:00:00ZFourier Decomposition of Polymer Orientation in Large-Amplitude Oscillatory Shear FlowGiacomin, A. JeffreyGilbert, Peter H.Schmalzer, Andrew M.http://hdl.handle.net/1974/127822015-03-17T14:58:37Z2015-03-17T04:00:00ZTitle: Fourier Decomposition of Polymer Orientation in Large-Amplitude Oscillatory Shear Flow
Authors: Giacomin, A. Jeffrey; Gilbert, Peter H.; Schmalzer, Andrew M.
Abstract: In our previous work, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in large-amplitude oscillatory shear flow, a flow experiment that has gained a significant following in recent years. We chose rigid dumbbells since these are the simplest molecular model to give higher harmonics in the components of the stress response. We derived the expression for the dumbbell orientation distribution, and then we used this function to calculate the shear stress response, and normal stress difference responses in large-amplitude oscillatory shear flow. In this paper, we deepen our understanding of the polymer motion underlying large-amplitude oscillatory shear flow by decomposing the orientation distribution function into its first five Fourier components (the zeroth, first, second, third and fourth harmonics). We use three-dimensional images to explore each harmonic of the polymer motion. Our analysis includes the three most important cases: (i) nonlinear steady shear flow (where the Deborah number λω is zero and the Weissenberg number λγ0 is above unity), (ii) nonlinear viscoelasticity (where both λω and λγ0 exceed unity), and (iii) linear viscoelasticity (where λω exceeds unity and where λγ0 approaches zero). We learn that the polymer orientation distribution is spherical in the linear viscoelastic regime, and otherwise, tilted and peanut-shaped. We find that the peanut-shaping is mainly caused by the zeroth harmonic, and the tilting, by the second. The first, third and fourth harmonics of the orientation distribution make only slight contributions to the overall polymer motion.2015-03-17T04:00:00ZPadé Approximants for Large-Amplitude Oscillatory Shear FlowGiacomin, A. JeffreySaengow, ChaimongkolGuay, MartinKolitawong, Chanyuthttp://hdl.handle.net/1974/127812015-03-17T14:41:25Z2015-03-17T04:00:00ZTitle: Padé Approximants for Large-Amplitude Oscillatory Shear Flow
Authors: Giacomin, A. Jeffrey; Saengow, Chaimongkol; Guay, Martin; Kolitawong, Chanyut
Abstract: Analytical solutions for either the shear stress or the normal stress differences in large-amplitude oscillatory shear flow, both for continuum or molecular models, often take the form of the first few terms of a power series in the shear rate amplitude. Here we explore improving the accuracy of these truncated series by replacing them with ratios of polynomials. Specifically, we examine replacing the truncated series solution for the corotational Maxwell model with its Padé approximants for the shear stress response, and for the normal stress
differences. We find these Padé approximants to agree closely with the corresponding exact solution, and that, in this way, we learn that in this way, one can nearly eliminate the inaccuracies of the truncated expansions.2015-03-17T04:00:00ZExact Analytical Solution for Large-Amplitude Oscillatory Shear FlowSaengow, ChaimongkolGiacomin, A. JeffreyKolitawong, Chanyuthttp://hdl.handle.net/1974/127792015-03-17T14:42:20Z2015-03-16T04:00:00ZTitle: Exact Analytical Solution for Large-Amplitude Oscillatory Shear Flow
Authors: Saengow, Chaimongkol; Giacomin, A. Jeffrey; Kolitawong, Chanyut
Abstract: When polymeric liquids undergo large-amplitude shearing oscillations, the shear stress responds as a Fourier series, the higher harmonics of which are caused by fluid nonlinearity. Previous work on large-amplitude oscillatory shear flow has produced analytical solutions for the first few harmonics of a Fourier series for the shear stress response (none beyond the fifth) or for the normal stress difference responses (none beyond the fourth) [JNNFM, 166, 1081 (2011)], but this growing subdiscipline of mathematical physics has yet to produce an exact solution. Here, we derive what we believe to be the first exact analytical solution for the response of the extra stress tensor in large-amplitude oscillatory shear flow. Our solution, unique and in closed form, includes both the normal
stress differences and the shear stress for both startup and alternance. We solve the corotational Maxwell model as a pair of nonlinear coupled ordinary differential equations, simultaneously. We choose the corotational Maxwell model because this two-parameter model ( η0 and λ ) is the simplest constitutive model relevant to large-amplitude oscillatory shear flow, and because it has previously been found to be accurate for molten plastics. By relevant we mean that the model predicts higher harmonics. We find good agreement between the
first few harmonics of our exact solution, and of our previous approximate expressions (obtained using the Goddard integral transform). Our exact solution agrees closely with the measured behavior for molten plastics, not only at alternance, but also in startup.2015-03-16T04:00:00Z