MMP-sensitive Hydrogels for Induction of Embryonic Stem Cell Differentiation

During embryonic development, the extracellular matrix plays a critical role in regulating the differentiation of embryonic stem cells into specific cell lineages. MMP-sensitive PEG hydrogel is a material that has the ability to be degraded by the cells themselves upon secretion of proteases called MMPs. This synthetic material presents a great potential for mimicking the extracellular matrix due to the numerous bio-active peptides that can be incorporated. The suitability of this gel with mouse embryonic stem cells (ESCs) was studied for the first time in this project and its ability of supporting angiogenesis from embryoid bodies (EBs) was investigated. I encapsulated EBs in MMP-sensitive gel containing RGD and/or Wnt5a peptide and showed that sprouting activity could occurred after 14 days culture in a specific media. Even though the nature of the sprouting cells could not be totally determined, a percentage of them was shown to express the endothelial marker CD31. I also demonstrated the positive effect of RGD on the viability of EBs by analyzing their morphology as well as monitoring the cell proliferation over time. In addition to RGD, Wnt5a-derived peptide was incorporated in the gel to investigate its ability to not only support but also to enhance angiogenic activity. Indeed, in previous studies, this protein was reported as a factor increasing motility and invasion of ESCs-derived endothelial cells. However, due to high variations in EBs responses, the effect of Wnt5a could not be emphasized. Even though those results need to be repeated and further experiments are required to answer many new questions, they point to promising prospects for tissue engineering in terms of designing synthetic material that can encapsulate stem cells and promote desired differentiation thanks to specific incorporated ligands