• Biomimetic extracellular matrix hydrogels to model and investigate conventional outflow cell biology under normal and simulated glaucomatous conditions

      Herberg, Samuel; Li, Haiyan (2022-06)
      Dysfunction of the conventional outflow pathway (comprised of the trabecular meshwork (TM) and adjacent Schlemm's canal (SC)) is the principal cause of elevated intraocular pressure in primary open-angle glaucoma. Other in vitro TM model systems cannot accurately mimic the cell-extracellular matrix (ECM) interface, limiting their use for investigating glaucoma pathology. In this dissertation, we report a novel biomimetic hydrogel by mixing donor-derived human TM (HTM) cells with ECM proteins found in the native tissue. We demonstrated that this HTM hydrogel system allowed for investigation of actin arrangement, ECM remodeling, cell contractility, and HTM stiffness on a simulated tissue level (Chapter 2). Furthermore, we showed that TGFβ2-induced ERK signaling negatively regulates Rho-associated kinase-mediated phospho-myosin light chain expression and HTM cell contractility when cultured on soft ECM hydrogels but not on glass (Chapter 3). YAP and TAZ are important mechanotransducers implicated in glaucoma pathogenesis. We demonstrated that YAP/TAZ activity was upregulated by transforming growth factor beta 2 (TGFβ2) in both HTM and HSC cells cultured on/in ECM hydrogels (Chapters 4 and 5). It is widely accepted that the glaucomatous TM/SC interface is stiffer. To mimic the stiffness difference between diseased and healthy tissue, we utilized two different methods. In Chapter 4, riboflavin was used to facilitate secondary UV crosslinking of collagen fibrils and stiffen the matrix. We showed that ECM stiffening elevated YAP/TAZ activity in HTM cells through modulating focal adhesions and cytoskeletal rearrangement. In Chapter 6, we developed an ECM-alginate hybrid hydrogel system, which allowed for on-demand control over matrix stiffness during the culture of cells. We found that the stiffened matrix increased nuclear YAP and filamentous-actin fibers in HSC cells, which was completely reversed by matrix softening. We further demonstrated that YAP/TAZ inhibition could rescue HTM/HSC cell dysfunction induced by either TGFβ2 or stiff matrix (Chapters 4, 5, and 6). Finally, we showed that pharmacologic YAP/TAZ inhibition had promising potential to improve outflow facility in an ex vivo mouse eye perfusion model (Chapter 6). Collectively, we have developed bioengineered ECM hydrogels for modeling and investigation of conventional outflow cell-ECM interactions under normal and simulated glaucomatous conditions.