Extracellular matrix stiffness and geometry: The impact on static and dynamic cellular systems in vitro and the treatment of tissue ischemia

Biologically relevant cell culture assays that can be adapted for high-throughput screening are very important for biopharmaceutical industry. Cellular material for such applications can represent static cultures that do not change over time, or dynamic (i.e. transformational) cultures based on pulripotent cells undergoing “cellular metamorphosis” and differentiating into a multitude of various descendant cell types – the process accompanied by formation of histologically complex tissues. Hydrogels being hydrophilic polymer-based adhesion matrices promote tissue-like microenvironments through tunable mechanical qualities and presentation of bioactive molecules. Moreover, hydrogel-based implants with controlled geometry can also be used for stem cell delivery and other therapeutic applications. This thesis investigates how main cell functions can be controlled by the matrix mechanical properties, with a goal to emulate physiological processes in vitro and potentiate stem cell treatments with appropriate bio-matrix design. First, I describe a method to promote advanced cardiomyogenic and endothelial differentiation within embryoid bodies through the control of three-dimensionality on collagen-polyacrylamide gels with tunable stiffness (Chapter 2). Next, the function of airway smooth muscle cells is investigated on substrates with physiological and pathological stiffnesses as it pertains to the cell adhesion, proliferation, calcium signaling and secretory function (Chapter 3). And finally, the impact of inner geometry is studied in cell-laden alginate based bio-patches designed to promote recovery of blood perfusion in a mouse model of hind limb ischemia (Chapter 4). The results of this thesis will be useful in attempts to recreate tissue environment in vitro for toxicity assays and in cell-based therapies of ischemic conditions via cell-laden-scaffold implantation