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UBC Theses and Dissertations

Glycocalyx engineering : development of biomaterials, ligation strategies and in vitro systems to modulate inflammation at the endothelial surface Siren, Erika


Residing at the interface between circulating blood and the vessel wall, the endothelial glycocalyx is a prominent regulator of the immune response. Existing as a highly complex, glycoprotein-rich brush-like structure on the surface of the endothelium, it dynamically regulates endothelial behavior by changing its architecture and chemical composition. As such, it is an interesting target for cell surface engineering (CSE), a methodology in which the cell surface is chemically or genetically tailored to modulate cellular behavior. Glycocalyx engineering can also be explored as a therapeutic iteration of CSE, as the breakdown of the glycocalyx plays a pivotal role in the immune regulated pathways that initiate organ damage and rejection at the blood vessel surface. Though a variety of preventative strategies have been developed to attenuate immune-mediated organ damage, none exist which actively reverse glycocalyx damage to re-initiate the native immunoprotective structure on the cell surface. In this body of work, we present new techniques and tools for engineering the glycocalyx surface with glycocalyx mimicking polymers. Architecturally defined, biocompatible polymers like hyperbranched polyglycerol (HPG), linear polyglycerol (LPG) and polyethylene glycol (PEG) were explored as promising candidates for recapitulating glycocalyx function as they are non-immunogenic and can be easily functionalized post-polymerization. Utilizing the enzyme tTGase in concert with Q-tagged polymers, we developed a CSE technique that mediates extensive and gentle attachment onto lysine substrates on the endothelial glycocalyx. Once attached to the cell surface, the polymers were able to re-establish the immunosuppressive barrier functions of the glycocalyx following breakdown. Next, we built upon the therapeutic efficacy of our strategy by introducing immunosuppressive sialic acids onto the LPG-Q scaffold. Endothelial cell surfaces engineered with α2,3 sialic acid-decorated glycopolymers provided a potent localized therapy which combined sterically driven immunocamouflage against leukocyte binding with sialic acid-mediated CD8+ T-cell and NK-cell inhibition. The immunosuppressive nature of this CSE strategy was also recapitulated in vivo using an arterial transplant model. Finally, we presented two new tools designed to improve the control over and assessment of glycocalyx engineering strategies in cell culture by re-directing CSE in the longitudinal direction and developing physiological relevant glycocalyx structures in vitro.

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