Though the heart is one of the first organs to develop during embryogenesis and the physical aspects of development are well documented, little is known of the molecular mechanisms that control heart development. BMP signaling has been implicated in cardiac development both in vivo and in vitro, the initial research focused on altering this pathway. BMP signaling belongs to the signaling superfamily of transforming growth factor-b (Tgf-(beta)). Further evidence from mouse knockout studies, reveals a critical role of signaling through the Tgf-(beta) receptors in which Tgf-(beta) 3-/- mice demonstrate congenital heart defects. Tgf-(beta) signaling is typically relayed through a tetramer complex composed of two Tgf-(beta) type II and two type I (ALK5) receptors. The signaling of this tetramer has recently been identified in the differentiation of epicardial and endocardial to mesenchyme. Proceeding experiments have demonstrated that knocking ALK5 out selectively in endocardium, myocardium, or epicardium does not interfere with normal cardiac muscle development in vivo. Sridurongrit suggest that ALK5 signaling is required for smooth muscle development and vascularization of the myocardium but not cardiomyocoyte development. Therefore the role of ALK5 signaling during cardiac development is studied int two pluripotent models, mouse embryonic stem cells and human induced pluripotent stem cells (hiPS) in this research to understand the role of this pathway in cardiogenesis. Further the ultimate goals of this research is to screen small molecules and develop protocols that direct diffentiation of pluripotent stem cells to mesoderm and ultimately a cardiomyocyte fate. There are two major differentiation events that occur as a pluripotent stem cell differentiates to a terminal state. The cell begins as a pluripotent cell that can give rise to all somatic cell types as this cell differentiates it enters multipotent stage. Multipotent cells become partially programmed and can give rise to only certain somatic fates. These multipotent progenitors will ultimately give rise to structured tissue composed of specific somatic cell types. However, the molecular pathways that control differentiation to specific somatic fates remain poorly understood. The focus of this research is to explore these pathways using small molecule inhibitors to better understand the internal cell signaling that controls cardiogenesis. The research presented in this paper occurs in two major stages. First the experiments focus on developing protocols that can induce pluripotent stem cells to give rise to mesoderm, the germ layer from which cardiomyocytes are derived. Secondly, small molecules are screened to understand their ability to drive this mesoderm to a cardiomyocyte fate. Exploring these pathways, that control cardiogenesis, is essential if stem cells are to provide a supply of primary cardiomycotes to better understand human cardiac physiology and the affect potential drugs will have on their function. Heart disease remains the number one cause of death in the developed world. Therefore there is not only a need to develop novel molecules that can assuage cardiac disease but there is also a need to understand how these diseases develop. hiPS have the potential to fulfill both these needs. These cells can be derived directly from patients with specific cardiac afflictions. By controlling the differentiation of these disease derived pluripotent cells, researchers will be able to track physical and chemical changes in cardiomyocyte development that ultimately lead to a diseased phenotype. This creates a powerful tool to study new molecules and cardiac disease. Screening of small molecules that alter the diseased phenotype of these patients will further understanding of chemical modulation of cardiomyocytes and the ability of potential drugs to mitigate disease. This research has the potential to ultimately lead to patient specific therapeutics in the treatment of heart disease.

Chemical and mechanical cues are known to guide the differentiation of pluripotent stem cells (PSCs) towards specific cell-types; a process known as directed differentiation. Typically, directed differentiation protocols to guide PSCs to specific cell types have focused on chemical cues. For example, lung epithelial directed differentiation protocols mimic the chemical cues observed in lung organogenesis. The products of current directed differentiation protocols are typically unorganized cellular aggregates that are often limited by their inability to generate specific cell types reliably. This suggests further improvements to these protocols are necessary for reliable cell manufacturing. Introducing developmentally relevant mechanical signals offers a potentially novel strategy to improve the predictability and reduce the heterogeneity of current directed differentiation protocols. To assess the feasibility of this concept we use polymeric substrates to guide the self-assembly of human PSC-derived lung progenitors into developmentally relevant sized tubes and assess the impact of defined architecture on differentiation. Specifically, day 17 ventralized lung progenitors, dual positive for proximal and distal lung markers SOX2 and SOX9, respectively, were cultured in polymeric tubes with diameters of 100μm and allowed to self-assemble into cellular tubes. Cells cultured in tubes were observed to become primarily SOX9+ as compared to cells in flat cultures that remained dual positive. Cells from tube cultures were retrieved and exposed to proximal or distal airway inducing conditions. Our data show that cells from flat culture are capable of expressing proximal and distal markers under proximal and distal conditions, respectively. However, cells retrieved from tubes were able to express distal markers under distal conditions but not proximal markers under proximal conditions. Our results suggest that modulation of tension in the presence of canonical WNT signaling by culturing the dual positive cells in the 100μm tubes resulted in loss of SOX2 expression. Overall, this thesis suggests that the use of a bioinspired mechanical microenvironment to organize and control the differentiation of developing lung epithelial populations during directed differentiation is a tractable strategy to control cellular differentiation in vitro.

Neural Surface Antigens: From Basic Biology towards Biomedical Applications focuses on the functionalrole of surface molecules in neural development, stem cell research, and translational biomedical paradigms.With an emphasis on human and rodent model systems, this reference covers fundamentals of neural stemcell biology and flow cytometric methodology. Addressing cell biologists as well as clinicians working in theneurosciences, the book was conceived by an international panel of experts to cover a vast array of particularsurface antigen families and subtypes. It provides insight into the basic biology and functional mechanisms ofneural cell surface signaling molecules influencing mammalian development, regeneration, and treatments. - Introduces early phase clinical trials of neural stem cells - Outlines characterization of surface molecule expression and methods for isolation which open unprecedented opportunities for functional study, quantitation & diagnostics - Highlights the role of stem cells in neural surface antigen and biomarker analysis and applications