Development of bioactive biomaterials for pluripotent stem cell arterial venous differentiation

Abstract

Within the framework of this thesis, we proposed to investigate ephrinB2/EphB4 signaling with respect to vascular and arterial venous pluripotent stem cell fate in vitro, specifically utilizing biomaterial approaches to mimic cell-cell signaling. PEG hydrogel photochemistry was optimized to create bioactive platforms with the potential to spatially-control the immobilization proteins or peptides. We successfully created distinct arterial venous EC populations derived from pluripotent stem cells using a combination of immobilized and soluble biochemical cues and thoroughly characterized these populations for phenotypic functionality. EphrinB2 signaling mechanisms during differentiation in vitro and furthermore how multivalency plays a role was explored. Overall, the findings of this thesis will help further our understandings of arterial venous specification, highlight the importance of phenotypic-specific ECs and provide novel biomaterial approaches to control stem cell fate.

Stem cell-derived endothelial cells (ECs) differentiated from pluripotent stem cells have potential in a variety of therapeutic applications including tissue engineered vascular grafts, re-vascularization of ischemic tissues, cardiovascular disease modeling and development of tissue engineering 3D constructs. There are many stimuli that influence pluripotent stem cell differentiation. Generally, stem cell engineers rely on soluble factors; however, there are limitations in this approach. These methods are unable to accurately display specific signaling motifs such as sequestered growth factors, multivalent interactions, cell-cell signaling and spatially specific patterns. Biomaterials provide a novel platform for providing immobilized signals to better mimic in vivo cell signaling. While many advances have contributed towards advancing the field of stem cell-derived endothelial cells (ECs), these are limited options in generation of phenotypic-specific populations, namely arterial and venous ECs. We know there are molecular distinctions between arteries and veins early in development, prior to hemodynamic cues. Specifically, ligand ephrinB2 is solely expressed on arterial ECs, while its receptor, EphB4 is solely expressed on venous ECs. EphrinB2/EphB4 bidirectional signaling plays an important role in vessel patterning, yet it is unknown whether this signaling contributes to phenotype specification.