Hydration-Dependent Structuring in the Cornea: A Model for Bound Water in Collagenous Tissues

Most mechanically competent connective tissues share similarities in their constitution, form and function. Most notably, they are comprised of a dense, hydrated extracellular matrix containing collagens and proteoglycans. Both of these constitutive elemen ts contribute to the structuring of connective tissues through macromolecular interactions mediated by interfacial forces in the aqueous medium that encompasses them. More specifically, these elements are arranged such that the swelling potential of proteo glycans is spatially confined by a relatively inextensible meshwork of collagen fibrils – leading to a system that exists in an equilibrium -like state of prestress. This prestress allows for the physiologic functioning and versatile viscoelastic properties that connective tissues exhibit. A consequence of this construction is that these elements bind large amounts of water at their interfaces, through the presentation of hydrophilic moieties, and are suscept ible to physical or chemical conditions that may affect their water binding affinity. Although well -understood as the driving phenomenon in the interactions of soluble globular proteins, this principle of bound interfacial water and its effect on the physi cal and morphological properties of hydrated connective tissues has not been extensively investigated in extracellular matrix biology. The studies contained within this thesis employ the cornea as an exemplary connective tissue model to study the role that bound water plays in influencing the form and function of such collagenous tissues. To do so, a coarse-grained multiscale model of corneal hydration was first developed to elucidate various confinement niches containing bound water to characterise both th e interactions and quantity of the bound water therein. Simultaneously, manipulation of factors influencing osmotic potential and osmolarity in corneas were employed to elucidate the relationship between bound water, hydration, and physicochemical properties of the bulk tissue. Finally, a multiscale microscopical analysis was performed to obtain a 3 -dimensional contextualized overview of the corneal structure in high resolution. Ultimately, these studies have begun to elucidate some of the important morpho logical and physicochemical dependent properties that hydrated connective tissues exhibit and paves the way for the development of new analytical methods to quantify and characterise this bound interfacial water.