UC Riverside

Open-Angle Glaucoma (OAG) is the leading cause of irreversible blindness. The cause of OAG is an increase in intraocular pressure, thought to be driven by fibrosis and other changes in the trabecular meshwork (TM). This accumulation is often the result of changes in the behavior of TM cells, which are responsible for maintaining the TM. In OAG, the cells are fewer in number, produce more extracellular matrix (ECM) proteins, and fail to remove ECM proteins and debris accumulation in the TM. Another change is mitochondrial damage, which takes the form of a decrease in mitochondrial DNA (mtDNA) per cell, an increase in the mitochondrial common deletion, and an increase in the damaged nucleotide 8-Oxo-2'-deoxyguanosine in mtDNA. This work sought to investigate the extent to which existing glaucoma models in TM cells affect mitochondrial performance and mtDNA damage. Further, this work also aimed to examine how mitochondrial DNA damage and depletion impacted levels of OAG-related transcripts. Dexamethasone (Dex) has been used to model glaucoma-like changes in TM cells. Specifically, it induces fibrotic changes in TM cells. In vivo, it can lead to glaucoma in humans and animal models. Our work shows that Dex leads to a decrease in ATP being produced by mitochondria in TM cells, as well as a decrease in mitochondrial performance. However, Dex treated TM cells did not show any evidence of the mtDNA damage found in OAG. For this reason, we next aimed to directly induce mtDNA damage and depletion in TM cells. Damage and depletion of mtDNA was induced by two methods, to account for potential off-target effects. One method was via treatment with ethidium bromide. In addition, another method involving doxycycline inducible expression of a mutant DNA repair enzyme was used as well. To allow for transduction and selection of cells with this construct, an immortalized version of TM cells was selected. Both of these methods yield a decrease in mtDNA per cell, as well a decrease in cytochrome c oxidase subunits. Interestingly, both models also yielded an increase in mRNA transcripts associated with OAG. This work indicates a relationship between a Dex-induced glaucoma model and an impairment of mitochondrial ATP production and performance. In addition, this work also indicates a potential relationship between mitochondrial DNA damage and an increase in glaucoma-related transcripts in TM cells. This could shed light on a new axis of OAG pathogenesis emanating from mitochondrial damage.