Stem cells are being widely researched for their therapeutic capabilities because they are an excellent source of self-renewing cells and have the potential to differentiate into any distinct cell type. With current reprogramming technologies available to generate clinically relevant stem cells, these cells are closer to being widely used for regenerative medicine therapies. However, a defined and non-xenogeneic system is required for obtaining clinically relevant stem cell cultures. Synthetic polymer substrates are generally hydrophobic and lack bioactive cell recognition sites, resulting in low cell adhesion and proliferation. As the extracellular matrix plays a crucial role in regulating cell behavior, synthetic polymer scaffolds have been fabricated to mimic the extracellular matrix. The signaling cues derived from the native and local microenvironment, specialized to maintain stem cell fate, are thought to be disrupted during aging and other pathophysiological conditions. Synthetic systems can incorporate individual signals of interest and thereby highlight the interaction between stem cells and their niche, by mimicking the altered stem cell niche and its microenvironmental cues during aging and pathophysiological conditions. Therefore, by understanding regulatory microenvironmental cues of the stem cell niche, we can gain a better understanding of changes occurring within the stem cell niche during aging and pathophysiological conditions and thereby provide more targeted therapy.
Overall, the work presented in this dissertation investigated how the addition of bioactive extracellular matrix peptides influences stem cell fate. In the first study, we studied the influence of synthetic polymer nanofibers on mouse embryonic stem cell differentiation. The results showed that the peptide-tethered nanofibers and soluble factors play an integrated role in the neural differentiation process, and that topography was less important in the cellular outcomes as nanofiber orientation did not influence neural differentiation. In the next study, we investigated whether a specific isoform of laminin supported neural stem cell (NSC) proliferation. We found laminin 511 was able to maintain NSC multipotency at a similar level to Matrigel, but for longer passages, and used this information to characterize the response of NSCs on hydrogel materials of different stiffness. We found that laminin 511 functionalized hydrogels maintained significantly high levels of multipotency compared to whole protein laminin and Arg-Gly-Glu (RGE) functionalized hydrogels. Overall, these studies demonstrated that shorter sequences of full-length laminin whole protein were able to illustrate specific interactions in vitro and provided a defined and controlled system in vitro. Therefore, we were able to investigate the influence of synthetic and immobilized microenvironmental cues on stem cell fate.
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