The overall goal is to determine the principle site of increased aqueous outflow resistance in primary open-angle glaucoma (POAG), a leading cause of blindness in the USA. As part of these studies, the applicant will evaluate how outflow resistance is generated in the normal human eye. It is conventionally believed that the JCT immediately underlying Schlemm's canal is responsible for the bulk of outflow resistance in the normal eye, and that changes in the extracellular matrix (ECM) in this region lead to glaucoma. However, there has been no direct proof of this proposition. Using quick-freeze/deep-etch morphological techniques, this group has now shown that the ECM in the JCT is more extensive than previously recognized, and can likely generate a significant fraction of aqueous outflow resistance in the normal human eye. An important aspect of this application is to use similar advanced morphological/morphometric techniques to determine whether the outflow resistance of the JCT is increased in POAG. This group and others have also shown that specific plasma-derived proteins can affect aqueous outflow resistance. They hypothesize that these proteins interact with the ECM in the JCT, leading to the extensive ultrastructural network seen using the quick-freeze/deep-etch techniques, and that POAG may result from excessive accumulation of these proteins in the JCT. The applicant will test this hypothesis, and will also examine other macromolecules found in the normal and glaucomatous JCT tissues, as viewed by quick-freeze/deep-etch. While their studies have implicated the JCT as responsible for generating the bulk of aqueous outflow resistance, they have also identified two types of pores in the inner wall of Schlemm's canal that may modulate juxtacanalicular flow resistance. In addition to changes in the JCT, glaucoma might be in part due to changes in one or both of these populations of inner wall pores. In this application, this possibility will be investigated. Exploiting the combined expertise in the areas of hydrodynamics, modeling, physiology, and ultrastructural and immunohistochemical methods, the studies proposed herein could significantly improve understanding of aqueous outflow resistance and its elevation in POAG.
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