Final Report Summary - BIOENGINEERED NICHES (Bioengineering the neural stem cell niche to identify regulators of fate determination)
While massive amount of research has been done to isolate and ex vivo culture stem cells, little attention has been put in trying to preserve these niche signals, despite the fact that they may be required to maintain stem cell functions (Lutolf et al., 2009). Stem cell isolation is feasible for many different tissues, however in vitro culture paradigms often consist of expansion of cells on plastic dishes, while extracellular signals are provided by addition of growth factors in solution, which very little match with the native environment. In many cases, this leads to rapid loss in culture of stem cell characteristics. Key examples are the culture of hematopoietic stem cells and muscle stem cells. By exploiting bioengineering techniques, we developed a novel cell culture platform to grow stem cells in vitro, by trying to emulate some key niche characteristics. Cells are cultured on soft hydrated gels (poly-ethylen-glycol hydrogels), largely consisting of water. By controlling the chemical composition of the gels, the stiffness of the substrate can be easily modified and the effect on stem cell behavior can be studied. The surface of these gels, contacting the cells, was modified in a way to provide signals: adhesion molecules, cell-cell contact signals and growth factors, that would mimic the native niche signals, from where the cells were extracted. This platform offered furthermore the possibility to systematically address, in a combinatorial fashion, which parameters would be more relevant in terms of achieving better proliferation or better differentiation of cells. Namely, protein concentrations and combinations could be easily modified (Gobaa et al., 2011). We combined this novel culture platform with time-lapse video microscopy, in order to obtain dynamic information on how the cell would respond to the environmental cues we provided. Monitoring cells continuously, instead of taking snap-shots in time of a culture, allows to better understand how the end point has been reached (Schroeder, 2011).