Modifications of poly(ethylene glycol)-based hydrogels for applications in tissue engineering and therapeutic angiogenesis
Moon, Jaehyun James
West, Jennifer L.
Doctor of Philosophy
In response to the rising demand for engineered tissues and organs, there have been great research interests to fabricate functional tissues in laboratories, and such products may revolutionize the current approaches for medicine and healthcare. However, to achieve this daunting task of mimicking functionality and complexity of native tissues, scaffolds have to be sufficiently vascularized with precise controls so that the resident cells can be perfused with oxygen and nutrients. The materials designed and cell culture techniques developed in this thesis demonstrate their capabilities to support endothelial cell (EC) culture and EC morphogenesis into capillary-like structures. Synthetic poly(ethylene-glycol) diacrylate (PEGDA) hydrogels are biomimetic scaffolds that can be specifically engineered with bioactive factors to allow favorable cell-matrix interactions. In this thesis, PEGDA hydrogel were fabricated with the Eph and ephrin family of proteins, and their angiogenic effects were assessed with human umbilical vein ECs (HUVECs). Ephrin-A1 immobilized on hydrogels promoted HUVEC adhesion and spreading in a dose-dependent manner, while EphB4 and ephrin-B2 stimulated them in a bi-phasic manner. EC adhesion and repulsion induced by either ephrin-A1, EphB4, or ephrin-B2 were found to be mediated by alphavbeta3 integrin. In particular, HUVECs cultured on the hydrogels with ephrin-A1 formed long tubular structures with patent lumens. This thesis introduces a photolithographic micropatterning technique to dictate local distribution of cell adhesive ligand, RGDS, in order to guide endothelial tubule formation. On these RGDS stripes, HUVECs reorganized their cell bodies into cord-like structures, and this angiogenic response was tightly controlled by the density and width of RGDS stripes, demonstrating the ability to guide angiogenesis by materials design. This thesis also reports development of collagenase-sensitive PEG hydrogels and their subsequent use to culture HUVECs and 10T1/2 cells, precursors to mural cell types, in 3D network of hydrogels. Whereas tubule-like structures formed in HUVEC monoculture conditions regressed rapidly, those formed in co-culture conditions with 10T1/2 cells were more elongated and stable. Furthermore, an optimal hydrogel formulation that maximized angiogenic responses in 3D was found and presented. The studies presented in this thesis demonstrate that endothelial angiogenesis can be promoted and regulated in synthetic, biomimetic scaffold materials by rational materials design.
Cell biology; Biomedical engineering